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Gain (loss) from cash and land contribution to a real estate venture.

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Number of real estate ventures.

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Area of a real estate property.

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This item represents an other than temporary decline in value that has been recognized against an investment accounted for under the equity method of accounting. The excess of the carrying amount over the fair value of the investment represents the amount of the write down which is or was reflected in earnings. The written down value is a new cost basis with the adjusted value of the investment becoming its new carrying value subject to the equity accounting method. Evidence of a loss in value might include, but would not necessarily be limited to, absence of an ability to recover the carrying amount of the investment or inability of the investee to sustain an earnings capacity which would justify the carrying amount of the investment.

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The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

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The net gain (loss) resulting from sales and other disposals of real estate owned for investment purposes.

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Amount of income (loss) for proportionate share of equity method investee's income (loss).

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Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

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- Definition

Amount of distribution received from equity method investee for return of investment, classified as investing activities. Excludes distribution for return on investment, classified as operating activities.

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Cash received from the sale of real estate that is held for investment, that is, it is part of an investing activity during the period.

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The amount of revenue derived from managing real estate properties.

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The carrying amount of investments in unconsolidated real estate and other joint ventures not separately presented. This includes direct and indirect investments.

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The cash outflow to repay long-term debt that is wholly or partially secured by collateral. Excludes repayments of tax exempt secured debt.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Investments in Unconsolidated Real Estate Ventures - Narrative (Details) $ in Thousands	1 Months Ended			3 Months Ended		12 Months Ended
	Jan. 31, 2022 USD ($)	Apr. 30, 2021 USD ($) ft² item	Dec. 31, 2019 USD ($) ft²	Jun. 30, 2021 USD ($)	Jun. 30, 2020 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($) ft²	Apr. 30, 2020 USD ($)
Schedule of Equity Method Investments [Line Items]
Gain (loss) on sale of real estate						$ 11,290	$ 59,477	$ 104,991
Proceeds from sale of real estate						14,370	154,493	377,511
Investments in unconsolidated real estate ventures						462,885	461,369
Income (loss) from unconsolidated real estate ventures, net						(2,070)	(20,336)	(1,395)
Distributions of capital from unconsolidated real estate ventures						$ 40,188	71,065	7,557
J.P. Morgan Global Alternatives ("J.P. Morgan")
Schedule of Equity Method Investments [Line Items]
Ownership interest (as percent)						50.00%
Investments in unconsolidated real estate ventures						$ 52,769
J.P. Morgan Global Alternatives ("J.P. Morgan") \| Potomac Yard Mixed Use Development
Schedule of Equity Method Investments [Line Items]
Number of real estate ventures \| item		2
Ownership interest (as percent)		50.00%
Area of real estate property \| ft²		2,000,000.0
Gain from contribution to real estate ventures		$ 11,300
Real estate venture promote interest paid				$ 17,500
J.P. Morgan Global Alternatives ("J.P. Morgan") \| Potomac Yard Mixed Use Development \| Non-employee Trustees and Certain Executives
Schedule of Equity Method Investments [Line Items]
Real estate venture promote interest paid				$ 4,200
J.P. Morgan Global Alternatives ("J.P. Morgan") \| Potomac Yard Landbay G
Schedule of Equity Method Investments [Line Items]
Area of real estate property \| ft²		700,000
J.P. Morgan Global Alternatives ("J.P. Morgan") \| Institutional Investor \| Potomac Yard Landbay F
Schedule of Equity Method Investments [Line Items]
Area of real estate property \| ft²		1,300,000
Investments in Unconsolidated Real Estate Ventures [Member]
Schedule of Equity Method Investments [Line Items]
Property management fee revenue						23,700	25,500	28,500
Landmark
Schedule of Equity Method Investments [Line Items]
Investments in unconsolidated real estate ventures						$ 28,298	66,724
Landmark \| Minimum
Schedule of Equity Method Investments [Line Items]
Ownership interest (as percent)						1.80%
Landmark \| Maximum
Schedule of Equity Method Investments [Line Items]
Ownership interest (as percent)						49.00%
Landmark \| L'Enfant Plaza
Schedule of Equity Method Investments [Line Items]
Impairment loss						$ 23,900
Landmark \| Rockville, Maryland [Member] \| Minimum \| Subsequent Event
Schedule of Equity Method Investments [Line Items]
Equity method investment ownership percentage sold	1.80%
Landmark \| Rockville, Maryland [Member] \| Maximum \| Subsequent Event
Schedule of Equity Method Investments [Line Items]
Equity method investment ownership percentage sold	18.00%
Landmark \| Landmark Venture Partner \| L'Enfant Plaza
Schedule of Equity Method Investments [Line Items]
Impairment loss						$ 48,700
Landmark \| Landmark Venture Partner \| Rockville, Maryland [Member] \| Subsequent Event
Schedule of Equity Method Investments [Line Items]
Proceeds from sale of real estate	$ 137,500
Repayments of secured debt	$ 79,800
Canadian Pension Plan Investment Board (CPPIB)
Schedule of Equity Method Investments [Line Items]
Ownership interest (as percent)						55.00%
Investments in unconsolidated real estate ventures						$ 48,498	47,522
Canadian Pension Plan Investment Board (CPPIB) \| 1101 17th Street [Member]
Schedule of Equity Method Investments [Line Items]
Investments in unconsolidated real estate ventures						$ 0	$ 0
Income (loss) from unconsolidated real estate ventures, net								$ 6,400
Canadian Pension Plan Investment Board (CPPIB) \| 1900 N Street [Member]
Schedule of Equity Method Investments [Line Items]
Distributions of capital from unconsolidated real estate ventures					$ 70,800
Canadian Pension Plan Investment Board (CPPIB) \| CPPIB Venture Partner \| 1900 N Street [Member]
Schedule of Equity Method Investments [Line Items]
Maximum borrowing capacity									$ 160,000
CIM/PacLife [Member]
Schedule of Equity Method Investments [Line Items]
Investments in unconsolidated real estate ventures					0
CIM/PacLife [Member] \| The Marriott Wardman Park hotel
Schedule of Equity Method Investments [Line Items]
Impairment loss					$ 6,500
Unconsolidated Real Estate Ventures \| Central Place Tower [Tower]
Schedule of Equity Method Investments [Line Items]
Ownership interest (as percent)			50.00%					50.00%
Area of real estate property \| ft²			552,000					552,000
Gain (loss) on sale of real estate								$ 53,400
Equity method investment ownership percentage sold			50.00%					50.00%
Proceeds from sale of real estate			$ 220,000					$ 220,000