Fair Value Measurements (Summary of Derivative Instruments) (Details) - USD ($)	Dec. 31, 2021	May 10, 2021	Dec. 31, 2020
Matures in May 2028 | Office Building | 555 California Street
Derivative [Line Items]
Equity method ownership percentage	70.00%	70.00%
Debt instrument, amount	$ 1,200,000,000	$ 1,200,000,000
Interest Rate Cap | Various interest rate caps | Other Assets | Designated as Hedging Instrument
Derivative [Line Items]
Derivative Asset, Fair Value	550,000		$ 17,000
Derivative Asset, Notional Amount	1,650,000,000		175,000,000
Interest Rate Swap | Other Assets | Designated as Hedging Instrument
Derivative [Line Items]
Derivative Asset, Fair Value	18,929,000
Derivative Asset, Notional Amount	2,990,000,000
Interest Rate Swap | Other Liabilities | Designated as Hedging Instrument
Derivative [Line Items]
Derivative Liability, Fair Value	32,837,000		66,033,000
Derivative Liability, Notional Amount	850,000,000		850,000,000
Interest Rate Swap | 555 California Mortgage Loan Interest Rate Swap | Other Assets | Designated as Hedging Instrument
Derivative [Line Items]
Derivative Asset, Fair Value	11,814,000
Derivative Asset, Notional Amount	$ 840,000,000
Derivative, Interest Rate	2.04%
Derivative, Swap Rate	2.26%
Interest Rate Swap | PENN 11 Interest Rate Swap | Other Assets | Designated as Hedging Instrument
Derivative [Line Items]
Derivative Asset, Fair Value	$ 6,565,000
Derivative Asset, Notional Amount	$ 500,000,000
Derivative, Interest Rate	2.05%
Derivative, Swap Rate	2.23%
Interest Rate Swap | Senior unsecured term loan | Other Liabilities | Designated as Hedging Instrument
Derivative [Line Items]
Derivative Liability, Fair Value	$ 28,976,000		57,723,000
Derivative Liability, Notional Amount	$ 750,000,000		$ 750,000,000
Derivative, Interest Rate	1.10%		1.15%
Derivative, Swap Rate	3.87%		3.87%
Interest Rate Swap | 33-00 Northern Boulevard mortgage loan interest rate swap | Other Liabilities | Designated as Hedging Instrument
Derivative [Line Items]
Derivative Liability, Fair Value	$ 3,861,000		$ 8,310,000
Derivative Liability, Notional Amount	$ 100,000,000		$ 100,000,000
Derivative, Interest Rate	1.91%		1.95%
Derivative, Swap Rate	4.14%		4.14%
Interest Rate Swap | LIBOR | 555 California Mortgage Loan Interest Rate Swap | Other Assets | Designated as Hedging Instrument
Derivative [Line Items]
Derivative, Average Basis Spread on Variable Rate	0.0193%
Interest Rate Swap | LIBOR | PENN 11 Interest Rate Swap | Other Assets | Designated as Hedging Instrument
Derivative [Line Items]
Derivative, Average Basis Spread on Variable Rate	0.0195%
Interest Rate Swap | LIBOR | Senior unsecured term loan | Other Liabilities | Designated as Hedging Instrument
Derivative [Line Items]
Derivative, Average Basis Spread on Variable Rate	0.01%		0.01%
Interest Rate Swap | LIBOR | 33-00 Northern Boulevard mortgage loan interest rate swap | Other Liabilities | Designated as Hedging Instrument
Derivative [Line Items]
Derivative, Average Basis Spread on Variable Rate	0.018%		0.018%
Floating | Interest Rate Swap | Senior unsecured term loan | Other Liabilities | Designated as Hedging Instrument
Derivative [Line Items]
Derivative Liability, Notional Amount			$ 50,000
Floating | Interest Rate Swap | LIBOR | Senior unsecured term loan | Other Liabilities | Designated as Hedging Instrument
Derivative [Line Items]
Derivative, Average Basis Spread on Variable Rate			1.00%