Investment in Unconsolidated Joint Ventures (Narrative) (Details) $ in Thousands														1 Months Ended	3 Months Ended			9 Months Ended
		Sep. 30, 2023 USD ($) ft²	Sep. 13, 2023 USD ($) ft²	Sep. 06, 2023 USD ($) ft²	Sep. 05, 2023 USD ($)	Jul. 28, 2023 USD ($) Integer	Jul. 27, 2023 USD ($)	Jun. 28, 2023	Jun. 27, 2023 USD ($)	Jun. 02, 2023	Apr. 21, 2023 ft² Year	Apr. 20, 2023 USD ($)	Jan. 31, 2023 USD ($) ft² a Vehicles Building	Aug. 13, 2023	Sep. 30, 2023 USD ($) ft²		Sep. 30, 2022 USD ($)	Sep. 30, 2023 USD ($) ft²		Sep. 30, 2022 USD ($)	Oct. 30, 2023 ft²	Sep. 12, 2023 USD ($)	Sep. 08, 2023 USD ($)	Sep. 01, 2023 ft²	Jun. 30, 2023 ft²	Jun. 05, 2023 USD ($) ft²	Jun. 04, 2023 USD ($)	May 02, 2023 USD ($)	Dec. 31, 2022 USD ($)
Schedule of Equity Method Investments [Line Items]
Interest and Other Income															$ 20,715		$ 3,728	$ 48,999		$ 6,151
Interest Rate Swap
Schedule of Equity Method Investments [Line Items]
Derivative, Notional Amount		$ 1,200,000													1,200,000			1,200,000										$ 1,200,000
Related Party
Schedule of Equity Method Investments [Line Items]
Related party note receivable		$ 88,807													$ 88,807			$ 88,807											$ 78,576
3 Hudson Boulevard [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Percentage		25.00%													25.00%			25.00%
Interest Expense, Long-Term Debt		$ 25,600
200 Fifth Avenue JV LLC
Schedule of Equity Method Investments [Line Items]
Ownership Percentage	[1]	26.69%													26.69%			26.69%
Impairment loss on investment															$ 33,400
Office Tower Developer LLC
Schedule of Equity Method Investments [Line Items]
Ownership Percentage		50.00%													50.00%			50.00%
Gateway Commons Complex [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Percentage		50.00%													50.00%			50.00%
Podium Developer LLC [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Percentage		50.00%													50.00%			50.00%
BP/CRF Metropolitan Square LLC [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Percentage	[2]	20.00%													20.00%			20.00%
Gain on Unconsolidated Joint Venture Investment			$ 35,800
Platform 16
Schedule of Equity Method Investments [Line Items]
Ownership Percentage	[1],[3]	55.00%													55.00%			55.00%
Impairment loss on investment															$ 155,200
capitlization rate															6.00%
Discount Rate															12.00%
360 PAS Holdco LLC
Schedule of Equity Method Investments [Line Items]
Ownership Percentage	[1],[4]	42.21%													42.21%			42.21%
Impairment loss on investment															$ 54,000
Safeco Plaza REIT LLC
Schedule of Equity Method Investments [Line Items]
Ownership Percentage	[1],[5]	33.67%													33.67%			33.67%
Impairment loss on investment															$ 29,900
Unconsolidated Joint Ventures [Member]
Schedule of Equity Method Investments [Line Items]
Impairment loss on investment															272,603	[6]	0	$ 272,603	[6]	0
Gain on Unconsolidated Joint Venture Investment															35,756	[7]	$ 0	$ 35,756	[7]	$ 0
Worldgate Drive | Unconsolidated Properties
Schedule of Equity Method Investments [Line Items]
Ownership Percentage													50.00%
Payments to Acquire Interest in Joint Venture													$ 17,000
Net Rentable Area (in sf) | ft²													350,000
Number of buildings | Building													2
Number of parking space | Vehicles													1,200
Area of Land | a													10
7750 Wisconsin Avenue [Member] | Unconsolidated Properties
Schedule of Equity Method Investments [Line Items]
Ownership Percentage											50.00%
Net Rentable Area (in sf) | ft²											734,000
Construction Loan												$ 252,600
Debt Instrument, Description of Variable Rate Basis										Term Secured Overnight Finance Rate (“SOFR”)	LIBOR	London interbank offered rate (“LIBOR”)
Debt Instrument, Basis Spread on Variable Rate											1.25%	1.25%
Extension Option (in years)											1	1
Number of extensions												2
7750 Wisconsin Avenue [Member] | Unconsolidated Properties | Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate
Schedule of Equity Method Investments [Line Items]
Debt Instrument, Basis Spread on Variable Rate										1.35%
500 North Capitol Street, NW | Unconsolidated Properties
Schedule of Equity Method Investments [Line Items]
Ownership Percentage																										30.00%
Net Rentable Area (in sf) | ft²																										231,000
Debt																										$ 105,000	$ 105,000
Debt, Weighted Average Interest Rate																										6.83%
500 North Capitol Street, NW | Unconsolidated Properties | Company's Share [Member] | Related Party
Schedule of Equity Method Investments [Line Items]
Related party note receivable																										$ 10,500
3 Hudson Boulevard [Member] | Unconsolidated Properties
Schedule of Equity Method Investments [Line Items]
Ownership Percentage								25.00%
Debt Instrument, Description of Variable Rate Basis								LIBOR	LIBOR
Debt Instrument, Basis Spread on Variable Rate								3.50%	3.50%
Debt									$ 80,000
Number of extensions								1	2
Extension Option (in days)									30 days
Extension Option Two (in days)									180 days
3 Hudson Boulevard [Member] | Unconsolidated Properties | Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate
Schedule of Equity Method Investments [Line Items]
Debt Instrument, Basis Spread on Variable Rate														3.61%
3 Hudson Boulevard [Member] | Unconsolidated Properties | Extended Maturity
Schedule of Equity Method Investments [Line Items]
Debt Instrument, Term								30 days
100 Causeway Street [Member] | Construction Loans
Schedule of Equity Method Investments [Line Items]
Extension Option (in years) | Integer						1
Debt						$ 336,600	$ 340,600
Repayments of Construction Loans Payable						$ 4,000
100 Causeway Street [Member] | Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate | Construction Loans
Schedule of Equity Method Investments [Line Items]
Debt Instrument, Basis Spread on Variable Rate						1.48%	1.60%
100 Causeway Street [Member] | Office Tower Developer LLC
Schedule of Equity Method Investments [Line Items]
Ownership Percentage						50.00%
100 Causeway Street [Member] | Extended Maturity | Construction Loans
Schedule of Equity Method Investments [Line Items]
Fiscal Period Duration						1 year
100 Causeway Street [Member] | Unconsolidated Properties
Schedule of Equity Method Investments [Line Items]
Net Rentable Area (in sf) | ft²																					634,000
Leased percentage																					95.00%
751 Gateway | Unconsolidated Properties
Schedule of Equity Method Investments [Line Items]
Ownership Percentage																								49.00%
Net Rentable Area (in sf) | ft²																								231,000
Leased percentage																								100.00%
Hub on Causeway - Podium | Unconsolidated Properties | Podium Developer LLC [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Percentage				50.00%
Net Rentable Area (in sf) | ft²				383,000
Leased percentage				94.00%
Debt Instrument, Basis Spread on Variable Rate				2.50%	2.35%
Extension Option (in years)				1
Debt				$ 154,300	$ 174,300
Repayments of Construction Loans Payable				$ 20,000
Derivative, Notional Amount																							$ 154,300
Derivative, Fixed Interest Rate																							7.35%
Metropolitan Square
Schedule of Equity Method Investments [Line Items]
Debt																						$ 420,000
Metropolitan Square | Senior Loans
Schedule of Equity Method Investments [Line Items]
Debt																						305,000
Metropolitan Square | Junior Loans
Schedule of Equity Method Investments [Line Items]
Debt																						$ 115,000
Metropolitan Square | Scenario, Plan
Schedule of Equity Method Investments [Line Items]
Debt Instrument, Unused Borrowing Capacity, Amount			100,000
Metropolitan Square | Scenario, Plan | Affiliated Entity
Schedule of Equity Method Investments [Line Items]
Loans and Leases Receivable, Loans in Process			$ 20,000
Metropolitan Square | Unconsolidated Properties | BP/CRF Metropolitan Square LLC [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Percentage			20.00%
Net Rentable Area (in sf) | ft²			657,000
Gain on Unconsolidated Joint Venture Investment			$ 35,800
Platform 16 | Unconsolidated Properties
Schedule of Equity Method Investments [Line Items]
Net Rentable Area (in sf) | ft²																									390,000
Platform 16 | Unconsolidated Properties | Platform 16
Schedule of Equity Method Investments [Line Items]
Ownership Percentage																									55.00%
360 Park Avenue South | 360 PAS Holdco LLC
Schedule of Equity Method Investments [Line Items]
Impairment loss on investment															$ 54,000
capitlization rate															5.50%
360 Park Avenue South | Unconsolidated Properties | 360 PAS Holdco LLC
Schedule of Equity Method Investments [Line Items]
Net Rentable Area (in sf) | ft²		450,000													450,000			450,000
200 Fifth Avenue | 200 Fifth Avenue JV LLC
Schedule of Equity Method Investments [Line Items]
Impairment loss on investment															$ 33,400
capitlization rate															5.00%
Discount Rate															8.00%
200 Fifth Avenue | Unconsolidated Properties
Schedule of Equity Method Investments [Line Items]
Net Rentable Area (in sf) | ft²		855,000													855,000			855,000
Safeco Plaza | Safeco Plaza REIT LLC
Schedule of Equity Method Investments [Line Items]
Impairment loss on investment															$ 29,900
capitlization rate															5.50%
Discount Rate															8.00%
Safeco Plaza | Unconsolidated Properties
Schedule of Equity Method Investments [Line Items]
Net Rentable Area (in sf) | ft²		779,000													779,000			779,000

[1] During the three months ended September 30, 2023, the Company recognized an other-than-temporary impairment loss on its investment.

[2] This entity is a VIE as of September 30, 2023 (See Note 2). During the three months ended September 30, 2023, the Company completed a restructuring of its ownership in Metropolitan Square, as described below in this Note 5 and Note 14.

[3] At December 31, 2022, this entity was a VIE.

[4] The Company’s ownership includes (1) a 35.79% direct interest in the joint venture, (2) an additional 5.837% indirect ownership in the joint venture, and (3) an additional 1% interest in each of the two entities through which each partner owns its interest in the joint venture. The Company’s partners will fund required capital until their aggregate investment is approximately 58% of all capital contributions; thereafter, the partners will fund required capital according to their percentage interests.

[5] The Company’s ownership includes (1) a 33.0% direct interest in the joint venture, and (2) an additional 1% interest in each of the two entities through which each partner owns its interest in the joint venture.

[6] During the three months ended September 30, 2023, the Company recognized an other-than-temporary impairment loss on its investments in Platform 16, 360 Park Avenue South, 200 Fifth Avenue and Safeco Plaza of approximately $155.2 million, $54.0 million, $33.4 million and $29.9 million respectively, as described below in this Note 5.

[7] During the three months ended September 30, 2023, the Company completed a restructuring of its ownership in Metropolitan Square, as described below in this Note 5.