Fair Value Measurements (Summary of Derivative Instruments) (Details) - USD ($)	Sep. 30, 2022	Dec. 31, 2021
Derivative [Line Items]
Long term debt	$ 2,559,169,000	$ 2,562,604,000
Matures in May 2028 \| 555 California Street \| Office
Derivative [Line Items]
Equity method ownership percentage	70.00%	70.00%
Debt instrument, amount	$ 1,200,000,000	$ 1,200,000,000
Designated as Hedging Instrument \| Other Assets
Derivative [Line Items]
Derivative asset, fair value	189,891,000	18,929,000
Designated as Hedging Instrument \| Other liabilities
Derivative [Line Items]
Derivative liability, fair value	0	32,837,000
Designated as Hedging Instrument \| 555 California Street mortgage loan \| Interest rate swaps
Derivative [Line Items]
Derivative asset, fair value	53,160,000	11,814,000
Derivative asset, notional amount	$ 840,000,000
All-In Swapped Rate	2.26%
Designated as Hedging Instrument \| 770 Broadway mortgage loan \| Interest rate swaps
Derivative [Line Items]
Derivative asset, fair value	$ 32,010,000	0
Derivative asset, notional amount	$ 700,000,000
All-In Swapped Rate	4.98%
Designated as Hedging Instrument \| 770 Broadway mortgage loan \| Interest rate swaps \| Secured Overnight Financing Rate (SOFR)
Derivative [Line Items]
Variable Rate Spread	2.25%
Designated as Hedging Instrument \| PENN 11 mortgage loan \| Interest rate swaps
Derivative [Line Items]
Derivative asset, fair value	$ 28,555,000	6,565,000
Derivative asset, notional amount	$ 500,000,000
All-In Swapped Rate	2.23%
Designated as Hedging Instrument \| Unsecured revolving credit facility \| Interest rate swaps
Derivative [Line Items]
Derivative asset, fair value	$ 26,759,000	0
Derivative asset, notional amount	$ 575,000,000
All-In Swapped Rate	3.88%
Designated as Hedging Instrument \| Unsecured revolving credit facility \| Interest rate swaps \| Secured Overnight Financing Rate (SOFR)
Derivative [Line Items]
Variable Rate Spread	1.15%
Designated as Hedging Instrument \| Unsecured term loan \| Interest rate swaps
Derivative [Line Items]
Derivative asset, fair value	$ 13,706,000
Derivative liability, fair value		(28,976,000)
Derivative asset, notional amount	$ 800,000,000
All-In Swapped Rate	4.05%
Designated as Hedging Instrument \| Unsecured term loan \| Interest rate swaps \| Other Assets
Derivative [Line Items]
Derivative asset, notional amount	$ 800,000,000
Designated as Hedging Instrument \| Unsecured term loan (effective October 2023) \| Interest rate swaps
Derivative [Line Items]
Derivative asset, fair value	8,864,000	0
Derivative asset, notional amount	$ 500,000,000
All-In Swapped Rate	4.39%
Designated as Hedging Instrument \| 100 West 33rd Street mortgage loan \| Interest rate swaps
Derivative [Line Items]
Derivative asset, fair value	$ 8,053,000	0
Derivative asset, notional amount	$ 480,000,000
All-In Swapped Rate	5.06%
Designated as Hedging Instrument \| 100 West 33rd Street mortgage loan \| Interest rate swaps \| Secured Overnight Financing Rate (SOFR)
Derivative [Line Items]
Variable Rate Spread	1.65%
Designated as Hedging Instrument \| 888 Seventh Avenue mortgage loan \| Interest rate swaps
Derivative [Line Items]
Derivative asset, fair value	$ 7,231,000	0
Derivative asset, notional amount	$ 200,000,000
All-In Swapped Rate	4.66%
Long term debt	$ 83,200,000
Designated as Hedging Instrument \| 888 Seventh Avenue mortgage loan \| Interest rate swaps \| LIBOR
Derivative [Line Items]
Variable Rate Spread	1.70%
Designated as Hedging Instrument \| 4 Union Square South mortgage loan \| Interest rate swaps
Derivative [Line Items]
Derivative asset, fair value	$ 3,960,000
Derivative liability, fair value		(3,861,000)
Derivative asset, notional amount	$ 100,000,000
All-In Swapped Rate	3.74%
Designated as Hedging Instrument \| 4 Union Square South mortgage loan \| Interest rate swaps \| Other Assets
Derivative [Line Items]
Derivative asset, notional amount	$ 100,000,000
Designated as Hedging Instrument \| 4 Union Square South mortgage loan \| Interest rate swaps \| Other Assets \| Floating After January 2025
Derivative [Line Items]
Derivative liability, notional amount	$ 20,000,000
Designated as Hedging Instrument \| 4 Union Square South mortgage loan \| Interest rate swaps \| Other Assets \| Secured Overnight Financing Rate (SOFR) \| Floating After January 2025
Derivative [Line Items]
Rate	1.50%
Designated as Hedging Instrument \| 1290 Avenue of the Americas mortgage loan \| Interest rate swaps
Derivative [Line Items]
Cap strike rate	4.00%
Designated as Hedging Instrument \| 1290 Avenue of the Americas mortgage loan \| Interest Rate Cap
Derivative [Line Items]
Derivative asset, fair value	$ 6,304,000	411,000
Derivative asset, notional amount	950,000,000
Designated as Hedging Instrument \| Various mortgage loans \| Interest Rate Cap
Derivative [Line Items]
Derivative asset, fair value	1,289,000	139,000
Designated as Hedging Instrument \| Unsecured Term Loan Expiring October 2023 \| Interest rate swaps
Derivative [Line Items]
Derivative asset, notional amount	750,000,000
Designated as Hedging Instrument \| Unsecured Term Loan Maturing August 2027 \| Interest rate swaps
Derivative [Line Items]
Derivative asset, notional amount	$ 50,000,000
All-In Swapped Rate	4.04%
Designated as Hedging Instrument \| Unsecured Term Loan Maturing August 2027 \| Interest rate swaps \| Secured Overnight Financing Rate (SOFR)
Derivative [Line Items]
Variable Rate Spread	1.30%
Designated as Hedging Instrument \| Unsecured Term Loan Swapped Rate Through October 2026 \| Interest rate swaps
Derivative [Line Items]
Derivative asset, notional amount	$ 500,000,000
Designated as Hedging Instrument \| Unsecured Term Loan Portion Swapped \| Interest rate swaps
Derivative [Line Items]
Derivative asset, notional amount	$ 550,000,000
All-In Swapped Rate	4.36%
Designated as Hedging Instrument \| Unsecured Term Loan Portion Swapped \| Interest rate swaps \| Secured Overnight Financing Rate (SOFR)
Derivative [Line Items]
Variable Rate Spread	1.30%
Designated as Hedging Instrument \| 33‑00 Northern Boulevard Mortgage Loan \| Interest rate swaps \| Other liabilities
Derivative [Line Items]
Derivative liability, notional amount	$ 120,000,000
Designated as Hedging Instrument \| 33‑00 Northern Boulevard Mortgage Loan \| Interest rate swaps \| Other liabilities \| Floating After January 2025
Derivative [Line Items]
Derivative liability, notional amount		$ 100,000,000

Face (par) amount of debt instrument at time of issuance.

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Fixed interest rate related to the interest rate derivative.

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