Investments in Unconsolidated Joint Ventures (Investments in Unconsolidated Joint Ventures) (Details) - USD ($) $ in Thousands			12 Months Ended
		Jan. 08, 2024	Dec. 31, 2023	Dec. 14, 2023	Dec. 31, 2022
Schedule of Equity Method Investments [Line Items]
Other Liabilities			$ (445,947)		$ (450,918)
Investments in unconsolidated joint ventures			1,377,319		1,715,911
Investments In Affiliates Subsidiaries Associates And Joint Ventures net	[1]		1,337,416		1,630,485
Unconsolidated Joint Ventures [Member]
Schedule of Equity Method Investments [Line Items]
Other Liabilities			$ (39,900)		(85,400)
Square 407 Limited Partnership [Member]
Schedule of Equity Method Investments [Line Items]
Properties			Market Square North
Ownership Percentage			50.00%
Other Liabilities	[1]		$ (5,996)		$ (6,198)
BP/CRF Metropolitan Square LLC [Member]
Schedule of Equity Method Investments [Line Items]
Properties			Metropolitan Square
Ownership Percentage	[2]				20.00%
Other Liabilities	[1]				$ (37,629)
901 New York Avenue LLC [Member]
Schedule of Equity Method Investments [Line Items]
Properties			901 New York Avenue
Ownership Percentage	[3]		25.00%
Other Liabilities	[1]		$ (11,764)		$ (12,493)
901 New York Avenue LLC (economic ownership) [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Percentage			50.00%		50.00%
WP Project Developer LLC [Member]
Schedule of Equity Method Investments [Line Items]
Properties			Wisconsin Place Land and Infrastructure
Ownership Percentage	[4]		33.33%
Investments in unconsolidated joint ventures	[1]		$ 30,375		$ 31,971
500 North Capitol Venture LLC [Member]
Schedule of Equity Method Investments [Line Items]
Properties			500 North Capitol Street, NW
Ownership Percentage			30.00%
Other Liabilities	[1]		$ (10,253)		(9,185)
501 K Street LLC [Member]
Schedule of Equity Method Investments [Line Items]
Properties			1001 6th Street
Ownership Percentage			50.00%
Investments in unconsolidated joint ventures	[1]		$ 44,774		42,922
Podium Developer LLC [Member]
Schedule of Equity Method Investments [Line Items]
Properties			The Hub on Causeway - Podium
Ownership Percentage			50.00%
Investments in unconsolidated joint ventures	[1]		$ 45,201		46,839
Residential Tower Developer LLC [Member]
Schedule of Equity Method Investments [Line Items]
Properties			Hub50House
Ownership Percentage			50.00%
Investments in unconsolidated joint ventures	[1]		$ 40,235		45,414
Hotel Tower Developer LLC [Member]
Schedule of Equity Method Investments [Line Items]
Properties			The Hub on Causeway - Hotel Air Rights
Ownership Percentage			50.00%
Investments in unconsolidated joint ventures	[1]		$ 13,494		12,366
Office Tower Developer LLC
Schedule of Equity Method Investments [Line Items]
Properties			100 Causeway Street
Ownership Percentage			50.00%
Investments in unconsolidated joint ventures	[1]		$ 57,660		59,716
1265 Main Office JV LLC [Member]
Schedule of Equity Method Investments [Line Items]
Properties			1265 Main Street
Ownership Percentage			50.00%
Investments in unconsolidated joint ventures	[1]		$ 3,585		3,465
BNY Tower Holdings LLC [Member]
Schedule of Equity Method Investments [Line Items]
Properties			Dock 72
Ownership Percentage	[5]		50.00%
Other Liabilities	[1]		$ (11,890)		(19,921)
CA-Colorado Center LLC[Member]
Schedule of Equity Method Investments [Line Items]
Properties			Colorado Center
Ownership Percentage			50.00%
Investments in unconsolidated joint ventures	[1]		$ 237,815		233,862
7750 Wisconsin Avenue LLC [Member]
Schedule of Equity Method Investments [Line Items]
Properties			7750 Wisconsin Avenue
Ownership Percentage			50.00%
Investments in unconsolidated joint ventures	[1]		$ 50,064		52,152
BP-M 3HB Venture LLC [Member]
Schedule of Equity Method Investments [Line Items]
Properties			3 Hudson Boulevard
Ownership Percentage			25.00%
Investments in unconsolidated joint ventures	[1]		$ 115,103		$ 116,397
SMBP Venture LP [Member]
Schedule of Equity Method Investments [Line Items]
Properties			Santa Monica Business Park
Ownership Percentage	[6]				55.00%
Investments in unconsolidated joint ventures	[1]				$ 164,735
SMBP Venture LP [Member] | Joint Venture Partner [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Percentage				45.00%
Platform 16 Holdings LP [Member]
Schedule of Equity Method Investments [Line Items]
Properties			Platform 16
Ownership Percentage	[7],[8]		55.00%
Investments in unconsolidated joint ventures	[1]		$ 45,564		158,109
Gateway Portfolio Holdings LLC [Member]
Schedule of Equity Method Investments [Line Items]
Properties			Gateway Commons
Ownership Percentage			50.00%
Investments in unconsolidated joint ventures	[1]		$ 376,834		324,038
Rosecrans-Sepulveda Partners 4, LLC
Schedule of Equity Method Investments [Line Items]
Properties			Beach Cities Media Campus
Ownership Percentage			50.00%
Investments in unconsolidated joint ventures	[1]		$ 27,034		27,000
Safeco Plaza REIT LLC
Schedule of Equity Method Investments [Line Items]
Properties			Safeco Plaza
Ownership Percentage	[8],[9]		33.67%
Investments in unconsolidated joint ventures	[1]		$ 44,734		69,785
Safeco Plaza REIT LLC | Company's Share [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Percentage			33.00%
360 PAS Holdco LLC
Schedule of Equity Method Investments [Line Items]
Properties			360 Park Avenue South
Ownership Percentage	[8],[10]		71.11%
Investments in unconsolidated joint ventures			$ 42,988		$ 114,992	[1]
Number of Promote Entities					2
Payments to Acquire Real Estate and Real Estate Joint Ventures		$ 10,000
360 PAS Holdco LLC | Company's Share [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Percentage			35.79%		35.79%
360 PAS Holdco LLC | Joint Venture Partner [Member] | Scenario, Plan
Schedule of Equity Method Investments [Line Items]
Ownership Percentage			29.00%
PR II BXP Reston Gateway LLC
Schedule of Equity Method Investments [Line Items]
Properties			Skymark - Reston Next Residential
Ownership Percentage			20.00%
Investments in unconsolidated joint ventures	[1]		$ 15,184		$ 11,351
751 Gateway Holdings LLC
Schedule of Equity Method Investments [Line Items]
Properties			751 Gateway
Ownership Percentage			49.00%
Investments in unconsolidated joint ventures	[1]		$ 93,411		80,714
200 Fifth Avenue JV LLC
Schedule of Equity Method Investments [Line Items]
Properties			200 Fifth Avenue
Ownership Percentage	[8]		26.69%
Investments in unconsolidated joint ventures	[1]		$ 75,718		$ 120,083
ABXP Worldgate Investments LLC
Schedule of Equity Method Investments [Line Items]
Properties			13100 and 13150 Worldgate Drive
Ownership Percentage			50.00%
Investments in unconsolidated joint ventures	[1]		$ 17,546
Entity Owning Land And Infrastructure Of Project [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Percentage			33.33%
Safeco Partner Entity One [Member] | Company's Share [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Percentage			1.00%
Safeco Partner Entity Two | Company's Share [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Percentage			1.00%
360 Park Avenue South Partners Entity | Company's Share [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Percentage			1.00%		1.00%
360 Park Avenue South Partners Entity Two | Company's Share [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Percentage					1.00%
360 PAS Holdco LLC (indirect ownership)
Schedule of Equity Method Investments [Line Items]
Number of joint venture partner(s)				1
360 PAS Holdco LLC (indirect ownership) | Company's Share [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Percentage			35.02%		5.837%

[1] Investments with deficit balances aggregating approximately $39.9 million and $85.4 million at December 31, 2023 and December 31, 2022, respectively, are included within Other Liabilities in the Company’s Consolidated Balance Sheets.

[2] During the year ended December 31, 2023, the Company completed a restructuring of its ownership in Metropolitan Square, as described below in this Note 6.

[3] The Company’s economic ownership increased based on the achievement of certain return thresholds. At December 31, 2023 and December 31, 2022, the Company’s economic ownership was approximately 50%. On January 8, 2024, the Company’s joint venture partner transferred all of its interest in the joint venture to the Company for a gross purchase price of $10.0 million, see Note 17 for more information.

[4] The Company’s wholly-owned subsidiary that owns Wisconsin Place Office also owns a 33.33% interest in the joint venture entity that owns the land, parking garage and infrastructure of the project.

[5] This property includes net equity balances from the amenity joint venture.

[6] During the year ended December 31, 2023, the Company completed the acquisition of its joint venture partner’s 45% ownership interest in Santa Monica Business Park, as described below in this Note 6 and Note 3.

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

[8] During the year ended December 31, 2023, the Company recognized an other-than-temporary impairment loss on its investment.

[9] 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.

[10] On December 14, 2023, the Company completed the acquisition of all of one of its joint venture partners ownership interest. As a result of this acquisition, at December 31, 2023, the Company’s ownership includes (1) a 35.79% direct interest in the joint venture, (2) an additional 35.02% indirect ownership in the joint venture, and (3) an additional 1% interest in the entity through which the partner owns its interest in the joint venture. The Company’s partner will fund required capital until its aggregate investment is approximately 29% of all capital contributions; thereafter, the partners will fund required capital according to their percentage interests. At December 31, 2022, the Company’s ownership included (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.