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Investments in Unconsolidated Joint Ventures (Investments in Unconsolidated Joint Ventures) (Details) $ in Thousands | 9 Months Ended |  |  |  |  |
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Sep. 30, 2021 USD ($) ft² payments | Sep. 01, 2021 | Aug. 31, 2021 | Mar. 30, 2021 | Feb. 25, 2021 | Dec. 31, 2020 USD ($)
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |
Other Liabilities |  | $ (370,403) |  |  |  |  |  | $ (412,084) |
Investments in unconsolidated joint ventures |  | 1,373,522 |  |  |  |  |  | 1,310,478 |
Investments In Affiliates Subsidiaries Associates And Joint Ventures net | [1] | 1,336,947 |  |  |  |  |  | 1,273,919 |
Unconsolidated Joint Ventures [Member] |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |
Other Liabilities |  | $ (36,600) |  |  |  |  |  | (36,600) |
Square 407 Limited Partnership [Member] |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |
Properties |  | Market Square North |  |  |  |  |  |  |
Ownership Percentage |  | 50.00% |  |  |  |  |  |  |
Other Liabilities | [1] | $ (1,917) |  |  |  |  |  | (3,766) |
BP/CRF Metropolitan Square LLC [Member] |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |
Properties |  | Metropolitan Square |  |  |  |  |  |  |
Ownership Percentage |  | 20.00% |  |  |  |  |  |  |
Other Liabilities | [1] | $ (14,568) |  |  |  |  |  | (13,584) |
901 New York Avenue LLC [Member] |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |
Properties |  | 901 New York Avenue |  |  |  |  |  |  |
Ownership Percentage | [2] | 25.00% |  |  |  |  |  |  |
Other Liabilities | [1] | $ (12,390) |  |  |  |  |  | $ (12,264) |
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 | [3] | 33.33% |  |  |  |  |  |  |
Investments in unconsolidated joint ventures | [1] | $ 34,104 |  |  |  |  |  | $ 35,297 |
Annapolis Junction NFM, LLC [Member] |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |
Properties |  | Annapolis Junction |  |  |  |  |  |  |
Ownership Percentage |  |  |  |  |  | 50.00% |  | 50.00% | [4]
Investments in unconsolidated joint ventures | [1] |  |  |  |  |  |  | $ 13,463 |
540 Madison Venture |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |
Properties |  | 540 Madison Avenue |  |  |  |  |  |  |
Ownership Percentage | [5] | 60.00% |  |  |  |  |  |  |
Investments in unconsolidated joint ventures | [1] |  |  |  |  |  |  | 122 |
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] | $ (7,700) |  |  |  |  |  | (6,945) |
501 K Street LLC [Member] |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |
Properties |  | 1001 6th Street |  |  |  |  |  |  |
Ownership Percentage | [6] | 50.00% |  |  |  |  |  |  |
Investments in unconsolidated joint ventures | [1] | $ 42,669 |  |  |  |  |  | 42,499 |
Potential additonal payments to joint venture partner | payments |  | 2 |  |  |  |  |  |  |
Minimum square footage to make a potential additional payment to joint venture partner (in sqft) | ft² |  | 520,000 |  |  |  |  |  |  |
Podium Developer LLC [Member] |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |
Properties |  | The Hub on Causeway - Podium |  |  |  |  |  |  |
Ownership Percentage |  | 50.00% |  |  | 50.00% |  |  |  |
Investments in unconsolidated joint ventures | [1] | $ 48,970 |  |  |  |  |  | 48,818 |
Residential Tower Developer LLC [Member] |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |
Properties |  | Hub50House |  |  |  |  |  |  |
Ownership Percentage |  | 50.00% |  |  |  |  |  |  |
Investments in unconsolidated joint ventures | [1] | $ 47,934 |  |  |  |  |  | 50,943 |
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] | $ 11,402 |  |  |  |  |  | 10,754 |
Office Tower Developer LLC [Member] |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |
Properties |  | 100 Causeway Street |  |  |  |  |  |  |
Ownership Percentage |  | 50.00% |  |  |  |  |  |  |
Investments in unconsolidated joint ventures | [1] | $ 56,714 |  |  |  |  |  | 56,312 |
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] | $ 3,855 |  |  |  |  |  | 3,787 |
BNY Tower Holdings LLC [Member] |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |
Properties |  | Dock 72 |  |  |  |  |  |  |
Ownership Percentage |  | 50.00% |  |  |  |  |  |  |
Investments in unconsolidated joint ventures | [1] | $ 28,079 |  |  |  |  |  | 29,536 |
BNYA Amenity Operator LLC [Member] |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |
Properties |  | Dock 72 |  |  |  |  |  |  |
Ownership Percentage |  | 50.00% |  |  |  |  |  |  |
Investments in unconsolidated joint ventures | [1] | $ 1,151 |  |  |  |  |  | 1,846 |
CA-Colorado Center Limited Partnership [Member] |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |
Properties |  | Colorado Center |  |  |  |  |  |  |
Ownership Percentage |  | 50.00% |  |  |  |  |  |  |
Investments in unconsolidated joint ventures | [1] | $ 230,535 |  |  |  |  |  | 227,671 |
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] | $ 59,734 |  |  |  |  |  | 58,112 |
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] | $ 116,537 |  |  |  |  |  | 113,774 |
SMBP Venture LP [Member] |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |
Properties |  | Santa Monica Business Park |  |  |  |  |  |  |
Ownership Percentage |  | 55.00% |  |  |  |  |  |  |
Investments in unconsolidated joint ventures | [1] | $ 155,679 |  |  |  |  |  | 145,761 |
Platform 16 Holdings LP [Member] |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |
Properties |  | Platform 16 |  |  |  |  |  |  |
Ownership Percentage | [7] | 55.00% |  |  |  |  |  |  |
Investments in unconsolidated joint ventures | [1] | $ 108,098 |  |  |  |  |  | $ 108,393 |
Gateway Portfolio Holdings LLC [Member] |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |
Properties |  | Gateway Commons |  |  |  |  |  |  |
Ownership Percentage |  | 50.00% | [8] |  |  |  | 54.00% | 55.00% |
Investments in unconsolidated joint ventures | [1] | $ 328,367 |  |  |  |  |  | $ 336,206 |
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] | $ 27,124 |  |  |  |  |  | $ 27,184 |
Entity Owning Land And Infrastructure Of Project [Member] |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |
Ownership Percentage |  | 33.33% |  |  |  |  |  |  |
Gateway Commons Complex prior to deferred contribution [Member] [Member] |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |
Ownership Percentage |  | 52.00% |  |  |  |  |  | 55.00% |
Safeco Plaza REIT LLC |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |
Properties |  | Safeco Plaza |  |  |  |  |  |  |
Ownership Percentage |  | 33.67% | [9] | 33.67% |  |  |  |  |
Investments in unconsolidated joint ventures | [1] | $ 72,570 |  |  |  |  |  |  |
Safeco Plaza REIT LLC | Company's Share [Member] |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |
Ownership Percentage |  |  |  | 33.00% |  |  |  |  |
Safeco Partner Entity Two | Company's Share [Member] |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |
Ownership Percentage |  |  |  | 1.00% |  |  |  |  |
Safeco Partner Entity One [Member] | Company's Share [Member] |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |
Ownership Percentage |  |  |  | 1.00% |  |  |  |  |
[1] | Investments with deficit balances aggregating approximately $36.6 million at September 30, 2021 and December 31, 2020 are included within Other Liabilities in the Company’s Consolidated Balance Sheets.
[2] | The Company’s economic ownership has increased based on the achievement of certain return thresholds. At September 30, 2021 and December 31, 2020, the Company’s economic ownership was approximately 50%.
[3] | 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.
[4] | On March 30, 2021, the Company sold its interest in the joint venture to the partner. See below for additional details.
[5] | T he 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 September 30, 2021.
[6] | Under the joint venture agreement for this land parcel, the partner will be entitled to up to two additional payments from the venture based on increases in total entitled square footage of the project above 520,000 square feet and achieving certain project returns at stabilization.
[7] | This entity is a VIE (See Note 2).
[8] | As a result of the partner’s deferred contribution, the Company owned an approximately 52% and 55% interest in the joint venture at September 30, 2021 and December 31, 2020, respectively. (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 (each, a “Safeco Partner Entity”) through which each partner owns its interest in the joint venture.
[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 (each, a “Safeco Partner Entity”) through which each partner owns its interest in the joint venture.

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