[X]	Annual Report Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934

[  ]	Transition Report Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934

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•	combined reports better reflect how management and investors view the business as a single operating unit;

•	combined reports enhance investors' understanding of the Company and the Operating Partnership by enabling them to view the business as a whole and in the same manner as management;

•	combined reports are more efficient for the Company and the Operating Partnership and result in savings in time, effort and expense; and

•	combined reports are more efficient for investors by reducing duplicative disclosure and providing a single document for their review.

•	Item 6 - Selected Financial Data;

•	Item 9A - Controls and Procedures;

•	Item 15 - Certifications of CEO and CFO Pursuant to Sections 302 and 906 of the Sarbanes-Oxley Act;

•	Consolidated Financial Statements; and

•	the following Notes to Consolidated Financial Statements:

•	Note 11 - Equity;

•	Note 16 - Earnings Per Share and Per Unit; and

•	Note 19 - Quarterly Financial Data.

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•	owning high-quality, differentiated office buildings in the BBDs of our core markets;

•	improving the operating results of our properties through concentrated leasing, asset management, cost control and customer service efforts;

•	developing and acquiring office buildings in BBDs that improve the overall quality of our portfolio and generate attractive returns over the long term for our stockholders;

•	disposing of properties no longer considered to be core assets primarily due to location, age, quality and/or overall strategic fit; and

•	maintaining a balance sheet with ample liquidity to meet our funding needs and growth prospects.

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•	the unavailability of favorable financing;

•	construction costs exceeding original estimates;

•	construction and lease-up delays resulting in increased debt service expense and construction costs; and

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•	lower than anticipated occupancy rates and rents causing a property to be unprofitable or less profitable than originally estimated.

•	we could become engaged in a dispute with any of our joint venture partners that might affect our ability to develop or operate a property;

•	our joint ventures are subject to debt and the refinancing of such debt may require equity capital calls;

•	our joint venture partners may default on their obligations necessitating that we fulfill their obligation ourselves;

•	our joint venture partners may have different objectives than we have regarding the appropriate timing and terms of any renovation, sale or refinancing of properties;

•	our joint venture partners may be structured differently than us for tax purposes and this could create conflicts of interest; and

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•	our joint venture partners may have competing interests in our markets that could create conflicts of interest.

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•	disrupt the proper functioning of our networks and systems and therefore our operations and/or those of certain of our customers;

•	result in misstated financial reports, violations of loan covenants, missed reporting deadlines and/or missed permitting deadlines;

•	result in our inability to properly monitor our compliance with the rules and regulations regarding our qualification as a REIT;

•	result in the unauthorized access to, and destruction, loss, theft, misappropriation or release of, proprietary, confidential, sensitive or otherwise valuable information of ours or others, which others could use to compete against us or which could expose us to damage claims by third-parties for disruptive, destructive or otherwise harmful purposes and outcomes;

•	result in our inability to maintain the building systems relied upon by our customers for the efficient use of their leased space;

•	require significant management attention and resources to remedy any damages that result;

•	subject us to claims for breach of contract, damages, credits, penalties or termination of leases or other agreements; or

•	damage our reputation among our customers and investors generally.

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•	the level of institutional interest in us;

•	the perceived attractiveness of investment in us, in comparison to other REITs;

•	the attractiveness of securities of REITs in comparison to other asset classes;

•	our financial condition and performance;

•	the market's perception of our growth potential and potential future cash dividends;

•	government action or regulation, including changes in tax laws;

•	increases in market interest rates, which may lead investors to expect a higher annual yield from our distributions in relation to the price of our Common Stock;

•	changes in our credit ratings;

•	the issuance of additional shares of Common Stock, or the perception that such issuances might occur, including under our equity distribution agreements; and

•	any negative change in the level or stability of our dividend.

•	projections with respect to the future REIT taxable income expected to be generated by the Company;

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•	debt service requirements after taking into account debt covenants and the repayment and restructuring of certain indebtedness and the availability of alternative sources of debt and equity capital and their impact on our ability to refinance existing debt and grow our business;

•	scheduled increases in base rents of existing leases;

•	changes in rents attributable to the renewal of existing leases or replacement leases;

•	changes in occupancy rates at existing properties and execution of leases for newly acquired or developed properties;

•	changes in operating expenses;

•	anticipated leasing capital expenditures attributable to the renewal of existing leases or replacement leases;

•	anticipated building improvements; and

•	expected cash flows from financing and investing activities, including from the sales of assets generating taxable gains to the extent such assets are not sold in a tax-deferred exchange under Section 1031 of the Internal Revenue Code or another tax-free or tax-deferred transaction.

•	Ownership limit. The Company's charter prohibits direct, indirect or constructive ownership by any person or entity of more than 9.8% of the Company's outstanding capital stock. Any attempt to own or transfer shares of capital stock in excess of the ownership limit without the consent of the Company's board of directors will be void.

•	Preferred Stock. The Company's charter authorizes the board of directors to issue preferred stock in one or more classes and establish the preferences and rights of any class of preferred stock issued. These actions can be taken without

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Business combinations. Pursuant to the Company's charter and Maryland law, the Company cannot merge into or consolidate with another corporation or enter into a statutory share exchange transaction in which the Company is not the surviving entity or sell all or substantially all of its assets unless the board of directors adopts a resolution declaring the proposed transaction advisable and a majority of the stockholders voting together as a single class approve the transaction. Maryland law prohibits stockholders from taking action by written consent unless all stockholders consent in writing. The practical effect of this limitation is that any action required or permitted to be taken by the Company's stockholders may only be taken if it is properly brought before an annual or special meeting of stockholders. The Company's bylaws further provide that in order for a stockholder to properly bring any matter before a meeting, the stockholder must comply with requirements regarding advance notice. The foregoing provisions could have the effect of delaying until the next annual meeting stockholder actions that the holders of a majority of the Company's outstanding voting securities favor. These provisions may also discourage another person from making a tender offer for the Company's common stock, because such person or entity, even if it acquired a majority of the Company's outstanding voting securities, would likely be able to take action as a stockholder, such as electing new directors or approving a merger, only at a duly called stockholders meeting. Maryland law also establishes special requirements with respect to business combinations between Maryland corporations and interested stockholders unless exemptions apply. Among other things, the law prohibits for five years a merger and other similar transactions between a corporation and an interested stockholder and requires a supermajority vote for such transactions after the end of the five-year period. The Company's charter contains a provision exempting the Company from the Maryland business combination statute. However, we cannot assure you that this charter provision will not be amended or repealed at any point in the future.

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Control share acquisitions. Maryland general corporation law also provides that control shares of a Maryland corporation acquired in a control share acquisition have no voting rights except to the extent approved by a vote of two-thirds of the votes entitled to be cast on the matter, excluding shares owned by the acquirer or by officers or employee directors. The control share acquisition statute does not apply to shares acquired in a merger, consolidation or share exchange if the corporation is a party to the transaction, or to acquisitions approved or exempted by the corporation's charter or bylaws. The Company's bylaws contain a provision exempting from the control share acquisition statute any stock acquired by any person. However, we cannot assure you that this bylaw provision will not be amended or repealed at any point in the future.

•	Maryland unsolicited takeover statute. Under Maryland law, the Company's board of directors could adopt various anti-takeover provisions without the consent of stockholders. The adoption of such measures could discourage offers for the Company or make an acquisition of the Company more difficult, even when an acquisition would be in the best interest of the Company's stockholders.

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Anti‑takeover protections of operating partnership agreement. Upon a change in control of the Company, the partnership agreement of the Operating Partnership requires certain acquirers to maintain an umbrella partnership real estate investment trust structure with terms at least as favorable to the limited partners as are currently in place. For instance, the acquirer would be required to preserve the limited partner's right to continue to hold tax-deferred partnership interests that are redeemable for capital stock of the acquirer. Exceptions would require the approval of two-thirds of the limited partners of our Operating Partnership (other than the Company). These provisions may make a change of control transaction involving the Company more complicated and therefore might decrease the likelihood of such a transaction occurring, even if such a transaction would be in the best interest of the Company's stockholders.

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(1)	Annualized Cash Rental Revenue is cash rental revenue (base rent plus cost recovery income, excluding straight-line rent) from our office properties for the month of December 2017 multiplied by 12.

(1)	Annualized GAAP Rent Per Square Foot is rental revenue (base rent plus cost recovery income, including straight-line rent) for the month of December of the respective year multiplied by 12, divided by total occupied rentable square footage.

(2)	Annualized Cash Rent Per Square Foot is cash rental revenue (base rent plus cost recovery income, excluding straight-line rent) for the month of December of the respective year multiplied by 12, divided by total occupied rentable square footage.

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(1)	Annualized Cash Rental Revenue is cash rental revenue (base rent plus cost recovery income, excluding straight-line rent) for the month of December 2017 multiplied by 12.

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(1)	Expirations that have been renewed are reflected above based on the renewal expiration date. Expirations include leases related to completed not stabilized development properties but exclude leases related to developments in-process.

(2)	Annualized Cash Rental Revenue is cash rental revenue (base rent plus cost recovery income, excluding straight-line rent) for the month of December 2017 multiplied by 12.

(3)	Includes 98,000 rentable square feet of leases that are on a month-to-month basis, which represent 0.3% of total annualized cash rental revenue.

(1)	Includes deferred lease commissions which are classified in deferred leasing costs on our Consolidated Balance Sheets.

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(1)	Weighted Average Ownership Interest is calculated using Rentable Square Feet.

(2)	Annualized Cash Rental Revenue is cash rental revenue (base rent plus cost recovery income, excluding straight-line rent) for the month of December 2017 multiplied by 12.

(3)	Excluding our 26.5% ownership interest in a real estate brokerage services company.

(4)	This joint venture is consolidated.

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(1)	Includes a special cash dividend of $0.80 per share declared in the quarter ended December 31, 2016 and paid January 10, 2017. The principal purpose of the special dividend was to distribute taxable capital gains associated with the sales of substantially all of our wholly-owned Country Club Plaza assets in Kansas City (which we refer to as the “Plaza assets”) during the first quarter of 2016.

•	projections with respect to the future REIT taxable income expected to be generated by the Company;

•	debt service requirements after taking into account debt covenants and the repayment and restructuring of certain indebtedness and the availability of alternative sources of debt and equity capital and their impact on our ability to refinance existing debt and grow our business;

•	scheduled increases in base rents of existing leases;

•	changes in rents attributable to the renewal of existing leases or replacement leases;

•	changes in occupancy rates at existing properties and execution of leases for newly acquired or developed properties;

•	changes in operating expenses;

•	anticipated leasing capital expenditures attributable to the renewal of existing leases or replacement leases;

•	anticipated building improvements; and

•	expected cash flows from financing and investing activities, including from the sales of assets generating taxable gains to the extent such assets are not sold in a tax-deferred exchange under Section 1031 of the Internal Revenue Code or another tax-free or tax-deferred transaction.

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(1)	Includes a special cash dividend of $0.80 per share declared in the quarter ended December 31, 2016 and paid January 10, 2017.

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(1)	Includes a special cash distribution of $0.80 per unit declared in the quarter ended December 31, 2016 and paid January 10, 2017.

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•	the financial condition of our customers could deteriorate;

•	we may not be able to lease or re-lease second generation space, defined as previously occupied space that becomes available for lease, quickly or on as favorable terms as old leases;

•	we may not be able to lease newly constructed buildings as quickly or on as favorable terms as originally anticipated;

•	we may not be able to complete development, acquisition, reinvestment, disposition or joint venture projects as quickly or on as favorable terms as anticipated;

•	development activity in our existing markets could result in an excessive supply relative to customer demand;

•	our markets may suffer declines in economic and/or office employment growth;

•	unanticipated increases in interest rates could increase our debt service costs;

•	unanticipated increases in operating expenses could negatively impact our operating results;

•	we may not be able to meet our liquidity requirements or obtain capital on favorable terms to fund our working capital needs and growth initiatives or repay or refinance outstanding debt upon maturity; and

•	the Company could lose key executive officers.

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•	owning high-quality, differentiated office buildings in the BBDs of our core markets;

•	improving the operating results of our properties through concentrated leasing, asset management, cost control and customer service efforts;

•	developing and acquiring office buildings in BBDs that improve the overall quality of our portfolio and generate attractive returns over the long term for our stockholders;

•	disposing of properties no longer considered to be core assets primarily due to location, age, quality and/or overall strategic fit; and

•	maintaining a balance sheet with ample liquidity to meet our funding needs and growth prospects.

(1)	Weighted average per rentable square foot on an annual basis over the lease term.

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•	cash flow from operating activities;

•	bank term loans and borrowings under our revolving credit facility;

•	the issuance of unsecured debt;

•	the issuance of secured debt;

•	the issuance of equity securities by the Company or the Operating Partnership; and

•	the disposition of non-core assets.

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(1)	Excludes amortization of premiums, discounts, debt issuance costs and/or purchase accounting adjustments.

(2)

Consists primarily of commitments under signed leases and contracts for operating properties, excluding tenant-funded tenant improvements, and contracts for development/redevelopment projects. This includes $233.0 million of contractual commitments related to our in-process development activity, of which $189.6 million is scheduled to be funded in 2018. For a description of our development activity, see "Item 2. Properties - In-Process Development." The timing of these lease and contractual commitments may fluctuate.

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•	Real estate and related assets;

•	Impairments of real estate assets and investments in unconsolidated affiliates;

•	Sales of real estate;

•	Rental and other revenues; and

•	Allowance for doubtful accounts.

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•	Net income/(loss) computed in accordance with GAAP;

•	Less net income attributable to noncontrolling interests in consolidated affiliates;

•	Plus depreciation and amortization of depreciable operating properties;

•	Less gains, or plus losses, from sales of depreciable operating properties, plus impairments on depreciable operating properties and excluding items that are classified as extraordinary items under GAAP;

•	Plus or minus our share of adjustments, including depreciation and amortization of depreciable operating properties, for unconsolidated joint venture investments (to reflect funds from operations on the same basis); and

•	Plus or minus adjustments for depreciation and amortization and gains/(losses) on sales of depreciable operating properties, plus impairments on depreciable operating properties, and noncontrolling interests in consolidated affiliates related to discontinued operations.

(1)	Includes assumed conversion of all potentially dilutive Common Stock equivalents.

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•	activities undertaken and reports issued by employees responsible for testing our internal control over financial reporting;

•	quarterly sub-certifications by representatives from appropriate business and accounting functions to support the CEO's and CFO's evaluations of our controls and procedures;

•	other personnel in our finance and accounting organization;

•	members of our internal disclosure committee; and

•	members of the audit committee of the Company's Board of Directors.

•	pertain to the maintenance of records that in reasonable detail accurately and fairly reflect transactions and dispositions of assets;

•	provide reasonable assurance that transactions are recorded as necessary to permit preparation of financial statements in accordance with GAAP, and that receipts and expenditures are being made only in accordance with authorizations of management and directors; and

•	provide reasonable assurance regarding prevention or timely detection of unauthorized acquisition, use or disposition of assets that could have a material effect on the financial statements.

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•	fee simple title to the land underneath one of our buildings in Pittsburgh that was previously subject to a ground lease for a purchase price of $18.5 million. We expensed $0.5 million of acquisition costs (included in general and administrative expenses) related to this acquisition;

•	an acre of development land in Raleigh for a purchase price, including capitalized acquisition costs, of $5.8 million; and

•	14 acres of development land in Nashville for a purchase price, including capitalized acquisition costs, of $9.1 million.

•	a building in Tampa encompassing 528,000 rentable square feet for a net purchase price of $113.5 million and an adjacent land parcel for a purchase price of $2.2 million;

•	two buildings in Atlanta encompassing 896,000 rentable square feet for a net purchase price of $290.3 million;

•	land in Atlanta for a purchase price and related transaction costs of $5.2 million (including contingent consideration of $0.9 million); and

•	our Highwoods DLF 98/29, LLC joint venture partner’s 77.2% interest in a building in Orlando encompassing 168,000 rentable square feet in exchange for the assumption of secured debt recorded at fair value of $19.3 million (see Note 6).

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•	substantially all of our wholly-owned Country Club Plaza assets in Kansas City (which we refer to as the “Plaza assets”) for a sale price of $660.0 million (before closing credits to buyer of $4.8 million). We recorded gains on disposition of discontinued operations of $414.5 million and a gain on disposition of property of $1.3 million related to the land; and

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a 32,000 square foot building for a sale price of $4.7 million (before closing credits to buyer of $0.1 million) and recorded a gain on disposition of property of $1.1 million. The buyer, which leased 79% of the building, is a family business controlled by a director of the Company. The sale price exceeded the value set forth in an appraisal performed by a reputable independent commercial real estate services firm that has no relationship with the director or any of his affiliates.

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(1)	Our secured mortgage loans were collateralized by real estate assets with an aggregate undepreciated book value of $147.6 million at December 31, 2017. Our fixed rate mortgage loans generally are either locked out to prepayment for all or a portion of their term or are prepayable subject to certain conditions including prepayment penalties.

(2)	This debt was repaid in 2017.

(3)	Net of unamortized original issuance discount of $1.5 million and $1.9 million as of December 31, 2017 and 2016, respectively.

(4)	Net of unamortized original issuance discount of $1.3 million and $1.6 million as of December 31, 2017 and 2016, respectively.

(5)	Net of unamortized original issuance discount of $3.7 million as of December 31, 2017.

(6)	The interest rate was 2.46% at December 31, 2017.

(7)	As more fully described in Note 7, we entered into floating-to-fixed interest rate swaps that effectively fix LIBOR for $225.0 million of this loan. Accordingly, the equivalent fixed rate of this amount is 2.78%.

(8)	As more fully described in Note 7, we entered into floating-to-fixed interest rate swaps that effectively fix LIBOR for $50.0 million of this loan. Accordingly, the equivalent fixed rate of this amount is 2.79%. The interest rate on the remaining $150.0 million was 2.47% at December 31, 2017.

(9)	The interest rate was 2.60% at December 31, 2017.

(10)	The interest rate was 2.48% at December 31, 2017.

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•	available cash and cash equivalents;

•	cash flows from operating activities;

•	issuance of debt securities by the Operating Partnership (some of which debt securities may be hedged to a fixed interest rate pursuant to the forward-starting swaps referred to in Note 7);

•	issuance of secured debt;

•	bank term loans;

•	borrowings under our revolving credit facility;

•	issuance of equity securities by the Company or the Operating Partnership; and

•	the disposition of non-core assets.

7.	Derivative Financial Instruments

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7.	Derivative Financial Instruments - Continued

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8.	Commitments and Contingencies

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9.	Noncontrolling Interests

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10.	Disclosure About Fair Value of Financial Instruments

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10.	Disclosure About Fair Value of Financial Instruments - Continued

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11.	Equity

(1)	During 2016, cash dividends declared on Common Stock totaled $2.50 per share, of which approximately $0.06 was recognized as a 2017 distribution for federal income tax purposes.

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11.	Equity - Continued

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12.	Employee Benefit Plans

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12.	Employee Benefit Plans - Continued

(1)	Represents the interest rate as of the grant date on US treasury bonds having the same life as the estimated life of the option grants.

(2)	The dividend yield is calculated utilizing the then current regular dividend rate for a one-year period and the per share price of Common Stock on the date of grant.

(3)	Based on the historical volatility of Common Stock over a period relevant to the related stock option grant.

(4)	The average expected option life is based on an analysis of the Company's historical data.

(1)	The outstanding options at December 31, 2017 had a weighted average remaining life of 7.7 years.

(2)	The Company had 152,745 options exercisable at December 31, 2017 with a weighted average exercise price of $41.39, weighted average remaining life of 6.4 years and intrinsic value of $1.5 million. Of these exercisable options, there were no exercise prices higher than the market price of our Common Stock at December 31, 2017.

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12.	Employee Benefit Plans - Continued

(1)	The weighted average fair value at grant date of time-based restricted stock issued during the years ended December 31, 2017, 2016 and 2015 was $3.2 million, $3.2 million and $3.3 million, respectively.

(2)	The vesting date fair value of time-based restricted stock that vested during the years ended December 31, 2017, 2016 and 2015 was $4.1 million, $3.7 million and $3.9 million, respectively. Vested shares include those shares surrendered by employees to satisfy tax withholding obligations in connection with such vesting.

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12.	Employee Benefit Plans - Continued

(1)	Represents the interest rate as of the grant date on US treasury bonds having the same life as the estimated life of the total return-based restricted stock grants.

(2)	The dividend yield is calculated utilizing the then current regular dividend rate for a one-year period and the average per share price of Common Stock during the three-month period preceding the date of grant.

(3)	Based on the historical volatility of Common Stock over a period relevant to the related total return-based restricted stock grant.

(1)	The fair value at grant date of total return-based restricted stock issued during the years ended December 31, 2017, 2016 and 2015 was $2.4 million, $2.4 million and $2.5 million, respectively, at target.

(2)	The vesting date fair value of total return-based restricted stock that vested during the years ended December 31, 2017, 2016 and 2015 was $5.6 million, $3.1 million and $5.9 million, respectively, based on the performance of the specific plans. Vested shares include those shares surrendered by employees to satisfy tax withholding obligations in connection with such vesting.

(3)	The 2017, 2016 and 2015 amounts include 34,669, 6,647 and 61,860 additional shares, respectively, that were issued at the end of the applicable measurement period because actual performance exceeded certain levels of performance.

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12.	Employee Benefit Plans - Continued

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13.	Accumulated Other Comprehensive Income/(Loss)

(1)	Amounts reclassified out of accumulated other comprehensive income/(loss) into contractual interest expense.

14.	Rental and Other Revenues; Rental Property and Other Expenses

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15.	Real Estate and Other Assets Held For Sale and Discontinued Operations

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16.	Earnings Per Share and Per Unit

(1)	Includes all unvested restricted stock where dividends on such restricted stock are non-forfeitable.

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16.	Earnings Per Share and Per Unit - Continued

(1)	Includes all unvested restricted stock where distributions on such restricted stock are non-forfeitable.

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17.	Income Taxes

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18.	Segment Information

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18.	Segment Information - Continued

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18.	Segment Information - Continued

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19.	Quarterly Financial Data (Unaudited)

(1)	See Note 2 for a discussion regarding the sales of the Plaza assets.

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19.	Quarterly Financial Data (Unaudited) - Continued

(1)	See Note 2 for a discussion regarding the sales of the Plaza assets.

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20.	Subsequent Events

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(a)	Reconciliation of total real estate assets to balance sheet caption:

(b)	Reconciliation of total accumulated depreciation to balance sheet caption:

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(1)	The tax basis of aggregate land and buildings and tenant improvements as of December 31, 2017 is $4.8 billion.

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