Unconsolidated Real Estate Joint Venture Debt [Abstract]

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Area of a real estate property.

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Consolidated and unconsolidated real estate joint ventures - Unconsolidated real estate joint ventures (Details) $ in Thousands	3 Months Ended			9 Months Ended
	Sep. 30, 2021 USD ($) ft²	Sep. 30, 2020 USD ($)	Mar. 31, 2020 USD ($)	Sep. 30, 2021 USD ($) ft²	Sep. 30, 2020 USD ($)	Dec. 31, 2020 USD ($)
Schedule of Equity Method Investments
Investments in unconsolidated real estate joint ventures	$ 321,737			$ 321,737		$ 332,349
Impairment of real estate	$ 42,620	$ 7,680		$ 52,675	$ 22,901
Unconsolidated Real Estate Joint Ventures Debt
Interest Rate	3.27%			3.27%
Debt Balance at 100%	$ 9,263,587			$ 9,263,587
Equity Method Investee
Unconsolidated Real Estate Joint Ventures Debt
Debt Balance at 100%	918,265			918,265
Equity Method Investee \| Menlo Gateway
Schedule of Equity Method Investments
Investments in unconsolidated real estate joint ventures	$ 296,086			$ 296,086		300,622
Our ownership percentage (in percent)	49.00%			49.00%
Equity Method Investee \| 1655 and 1725 Third Street
Schedule of Equity Method Investments
Investments in unconsolidated real estate joint ventures	$ 14,093			$ 14,093		14,939
Our ownership percentage (in percent)	10.00%			10.00%
Equity Method Investee \| Other unconsolidated real estate joint ventures
Schedule of Equity Method Investments
Investments in unconsolidated real estate joint ventures	$ 11,558			$ 11,558		$ 16,788
Equity Method Investee \| 1401/1413 Research Boulevard
Schedule of Equity Method Investments
Investments in unconsolidated real estate joint ventures	$ 0		$ 0	$ 0
Area of real estate property \| ft²	90,000			90,000
Impairment of real estate			$ 7,600
Our ownership percentage (in percent)	65.00%			65.00%
Payments to acquire interest in joint venture				$ 578
Secured debt maturing on 5/17/22 \| Equity Method Investee \| 1401/1413 Research Boulevard
Unconsolidated Real Estate Joint Ventures Debt
Maturity Date				May 17, 2022
Interest Rate	3.50%			3.50%
Debt Balance at 100%	$ 27,145			$ 27,145
Secured debt maturing on 5/17/22 \| Equity Method Investee \| 1401/1413 Research Boulevard \| London Interbank Offered Rate (LIBOR)
Unconsolidated Real Estate Joint Ventures Debt
Stated interest rate (as a percent)	2.50%			2.50%
Secured debt maturing on 3/10/25 \| Equity Method Investee \| 1655 and 1725 Third Street
Unconsolidated Real Estate Joint Ventures Debt
Maturity Date				Mar. 10, 2025
Stated interest rate (as a percent)	4.50%			4.50%
Interest Rate	4.57%			4.57%
Debt Balance at 100%	$ 598,550			$ 598,550
Secured debt maturing on 5/1/35 \| Equity Method Investee \| Menlo Gateway
Unconsolidated Real Estate Joint Ventures Debt
Maturity Date				May 01, 2035
Stated interest rate (as a percent)	4.53%			4.53%
Interest Rate	4.59%			4.59%
Debt Balance at 100%	$ 154,992			$ 154,992
Secured debt maturing on 8/10/35 \| Equity Method Investee \| Menlo Gateway
Unconsolidated Real Estate Joint Ventures Debt
Maturity Date				Aug. 10, 2035
Stated interest rate (as a percent)	4.15%			4.15%
Interest Rate	4.18%			4.18%
Debt Balance at 100%	$ 137,578			$ 137,578