Debt - Long-Term Debt (Details)	6 Months Ended
	Jun. 30, 2023 USD ($)	May 18, 2023	Dec. 31, 2022 USD ($)
Debt Instrument [Line Items]
Outstanding borrowings	$ 0		$ 0
Total principal	2,261,361,000
Deferred financing costs, net	(14,542,000)		(16,720,000)
Adjustment benchmark		0.00114
Mortgages, senior notes, and unsecured term loan facilities, not including unsecured revolving credit facility
Debt Instrument [Line Items]
Total principal	2,261,361,000		2,265,630,000
Deferred financing costs, net	(10,619,000)		(11,748,000)
Unamortized debt discount	(7,354,000)		(7,745,000)
Total	2,243,388,000		2,246,137,000
Metro Center | Fixed rate mortgage debt
Debt Instrument [Line Items]
Fixed rate mortgage debt	$ 81,344,000		82,596,000
Stated Rate (as a percent)	3.59%
Effective Rate (as a percent)	3.67%
10 Union Square | Fixed rate mortgage debt
Debt Instrument [Line Items]
Fixed rate mortgage debt	$ 50,000,000		50,000,000
Stated Rate (as a percent)	3.70%
Effective Rate (as a percent)	3.97%
1542 Third Avenue | Fixed rate mortgage debt
Debt Instrument [Line Items]
Fixed rate mortgage debt	$ 30,000,000		30,000,000
Stated Rate (as a percent)	4.29%
Effective Rate (as a percent)	4.53%
First Stamford Place | Fixed rate mortgage debt
Debt Instrument [Line Items]
Fixed rate mortgage debt	$ 177,347,000		178,823,000
Stated Rate (as a percent)	4.28%
Effective Rate (as a percent)	4.73%
First Stamford Place - First Lien | Fixed rate mortgage debt
Debt Instrument [Line Items]
Stated Rate (as a percent)	4.09%
Face amount of debt instrument	$ 164,000,000
First Stamford Place - Second Lien | Fixed rate mortgage debt
Debt Instrument [Line Items]
Stated Rate (as a percent)	6.25%
Face amount of debt instrument	$ 13,300,000
1010 Third Avenue and 77 West 55th Street | Fixed rate mortgage debt
Debt Instrument [Line Items]
Fixed rate mortgage debt	$ 35,399,000		35,831,000
Stated Rate (as a percent)	4.01%
Effective Rate (as a percent)	4.21%
250 West 57th Street | Fixed rate mortgage debt
Debt Instrument [Line Items]
Fixed rate mortgage debt	$ 180,000,000		180,000,000
Stated Rate (as a percent)	2.83%
Effective Rate (as a percent)	3.21%
1333 Broadway | Fixed rate mortgage debt
Debt Instrument [Line Items]
Fixed rate mortgage debt	$ 160,000,000		160,000,000
Stated Rate (as a percent)	4.21%
Effective Rate (as a percent)	4.29%
345 East 94th Street - Series A(5) | Revolving credit facility | SOFR
Debt Instrument [Line Items]
Variable rate, effective percentage (as a percent)	70.00%
Basis spread on variable rate (as a percent)	0.95%
345 East 94th Street - Series A(5) | Fixed rate mortgage debt
Debt Instrument [Line Items]
Fixed rate mortgage debt	$ 43,600,000		43,600,000
Effective Rate (as a percent)	3.56%
345 East 94th Street - Series B(5) | Revolving credit facility | SOFR
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)	2.24%
345 East 94th Street - Series B(5) | Fixed rate mortgage debt
Debt Instrument [Line Items]
Fixed rate mortgage debt	$ 7,544,000		7,865,000
Effective Rate (as a percent)	3.56%
561 10th Avenue - Series A(5) | Revolving credit facility | SOFR
Debt Instrument [Line Items]
Variable rate, effective percentage (as a percent)	70.00%
Basis spread on variable rate (as a percent)	1.07%
561 10th Avenue - Series A(5) | Fixed rate mortgage debt
Debt Instrument [Line Items]
Fixed rate mortgage debt	$ 114,500,000		114,500,000
Effective Rate (as a percent)	3.85%
561 10th Avenue - Series B(5) | Revolving credit facility | SOFR
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)	2.45%
561 10th Avenue - Series B(5) | Fixed rate mortgage debt
Debt Instrument [Line Items]
Fixed rate mortgage debt	$ 16,627,000		17,415,000
Effective Rate (as a percent)	3.85%
Total mortgage debt | Fixed rate mortgage debt
Debt Instrument [Line Items]
Fixed rate mortgage debt	$ 896,361,000		900,630,000
Series A | Senior unsecured notes
Debt Instrument [Line Items]
Total	$ 100,000,000		100,000,000
Stated Rate (as a percent)	3.93%
Effective Rate (as a percent)	3.96%
Series B | Senior unsecured notes
Debt Instrument [Line Items]
Total	$ 125,000,000		125,000,000
Stated Rate (as a percent)	4.09%
Effective Rate (as a percent)	4.12%
Series C | Senior unsecured notes
Debt Instrument [Line Items]
Total	$ 125,000,000		125,000,000
Stated Rate (as a percent)	4.18%
Effective Rate (as a percent)	4.21%
Series D | Senior unsecured notes
Debt Instrument [Line Items]
Total	$ 115,000,000		115,000,000
Stated Rate (as a percent)	4.08%
Effective Rate (as a percent)	4.11%
Series E | Senior unsecured notes
Debt Instrument [Line Items]
Total	$ 160,000,000		160,000,000
Stated Rate (as a percent)	4.26%
Effective Rate (as a percent)	4.27%
Series F | Senior unsecured notes
Debt Instrument [Line Items]
Total	$ 175,000,000		175,000,000
Stated Rate (as a percent)	4.44%
Effective Rate (as a percent)	4.45%
Series G | Senior unsecured notes
Debt Instrument [Line Items]
Total	$ 100,000,000		100,000,000
Stated Rate (as a percent)	3.61%
Effective Rate (as a percent)	4.89%
Series H | Senior unsecured notes
Debt Instrument [Line Items]
Total	$ 75,000,000		75,000,000
Stated Rate (as a percent)	3.73%
Effective Rate (as a percent)	5.00%
Unsecured term loan facilities | Revolving credit facility
Debt Instrument [Line Items]
Outstanding borrowings	$ 215,000,000		215,000,000
Effective Rate (as a percent)	4.22%
Unsecured term loan facilities | Revolving credit facility | SOFR
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)	1.20%
Unsecured revolving credit facility | Revolving credit facility
Debt Instrument [Line Items]
Outstanding borrowings	$ 0		0
Effective Rate (as a percent)	0.00%
Unsecured revolving credit facility | Revolving credit facility | SOFR
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)	1.30%
Unsecured term loan facility | Revolving credit facility
Debt Instrument [Line Items]
Outstanding borrowings	$ 175,000,000		$ 175,000,000
Effective Rate (as a percent)	4.51%
Unsecured term loan facility | Revolving credit facility | SOFR
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)	1.50%