Investments in Unconsolidated Joint Ventures (Statements of Operations of the Joint Ventures) (Details) - USD ($) $ in Thousands			12 Months Ended
		Mar. 30, 2021	Dec. 31, 2021		Dec. 31, 2020		Dec. 31, 2019
Schedule of Equity Method Investments [Line Items]
Total revenue			$ 2,888,621		$ 2,765,686		$ 2,960,562
Expenses
Transaction costs			5,036		1,531		1,984
Depreciation and amortization			717,336		683,751		677,764
Total expenses			1,920,581		1,860,364		1,914,925
Other income (expense)
Interest expense			(423,346)		(431,717)		(412,717)
Gains on sales of real estate			123,660		618,982		709
Net income			631,932		1,018,691		651,999
Income (Loss) from Equity Method Investments			(2,570)		(85,110)		46,592
Straight-line rent adjustments			(104,300)		(104,900)		(58,400)
Above and below market rent adjustments, net			4,200		6,500		20,900
Write-off for accrued rent and accounts receivables			1,300		90,300
Unconsolidated Joint Ventures [Member]
Schedule of Equity Method Investments [Line Items]
Total revenue	[1]		383,649		319,560		322,817
Expenses
Operating			158,498		144,347		122,992
Transaction costs			470		1,027		1,000
Depreciation and amortization			147,121		141,853		102,296
Total expenses			306,089		287,227		226,288
Other income (expense)
Interest expense			(108,884)		(98,051)		(84,409)
Gains on sales of real estate			0		11,737	[2]	32,706	[2]
Net income			(31,324)		(53,981)		44,826
Company's share of net income			(10,254)		(16,256)		24,423
Gain on Sale of Investments			10,257	[3]	0		0
Impairment loss on investment			0		(60,524)	[4]	0
Basis differential	[5]		(2,573)		(8,330)	[2],[4]	22,169	[2]
Income (Loss) from Equity Method Investments			(2,570)		(85,110)		46,592
Straight-line rent adjustments			$ 17,200		$ (10,100)		32,400
540 Madison Avenue [Member]
Other income (expense)
Gains on sales of real estate							47,200
Ownership Percentage	[6]		60.00%
Annapolis Junction NFM, LLC [Member]
Other income (expense)
Gain on Sale of Investments		$ 10,300	$ 10,300
Ownership Percentage		50.00%			50.00%	[7]
Colorado Center [Member]
Other income (expense)
Straight-line rent adjustments			800		$ 1,800		2,100
Above and below market rent adjustments, net			$ 400		900		$ 1,700
Dock 72 [Member] | Unconsolidated Joint Ventures [Member]
Other income (expense)
Impairment loss on investment					$ (60,500)

[1] Includes straight-line rent adjustments of approximately $17.2 million, $(10.1) million and $32.4 million for the years ended December 31, 2021, 2020 and 2019, respectively

[2] For the year ended December 31, 2020, represents the gain on sale of Annapolis Junction Building Eight and two land parcels. For the year ended December 31, 2019, represents the gain on sale of 540 Madison Avenue recognized by the joint venture. During 2008, the Company recognized an other-than-temporary impairment loss on its investment in the unconsolidated joint venture resulting in a basis differential between the carrying value of the Company’s investment in the joint venture and the joint venture’s basis in the assets and liabilities of the property. As a result of the historical basis difference, the Company recognized a gain on sale of real estate totaling approximately $47.2 million for the year ended December 31, 2019, which consists of its share of the gain on sale reported by the joint venture as well as an adjustment for the basis differential. The gain on sale of real estate is included in Income (loss) from Unconsolidated Joint Ventures in the Company’s Consolidated Statements of Operations.

[3] During the year ended December 31, 2021, the Company completed the sale of its 50% ownership interest in Annapolis Junction NFM LLC. The Company recognized a gain on sale of investment of approximately $10.3 million.

[4] During the year ended December 31, 2020, the Company recognized an other-than-temporary impairment loss on its investment in the unconsolidated joint venture that owns Dock 72 in Brooklyn, New York totaling approximately $60.5 million.

[5] Includes straight-line rent adjustments of approximately $0.8 million, $1.8 million and $2.1 million for the years ended December 31, 2021, 2020 and 2019, respectively. Also includes net above-/below-market rent adjustments of approximately $0.4 million, $0.9 million and $1.7 million for the years ended December 31, 2021, 2020 and 2019, respectively.

[6] The property was sold on June 27, 2019. As of December 31, 2020, the investment consisted of undistributed cash. All remaining cash has been distributed as of December 31, 2021 and the joint venture has been dissolved.

[7] On March 30, 2021, the Company sold its interest in the joint venture to the partner. See below for additional details.