Revenue Recognition - Revenue by Segment (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Disaggregation of Revenue [Line Items]
Lease income									$ 1,719,710
Total revenues	$ 460,968	$ 465,961	$ 463,103	$ 534,668	$ 543,417	$ 542,048	$ 541,818	$ 536,437	1,924,700	$ 2,163,720	$ 2,084,126
Rental revenues
Disaggregation of Revenue [Line Items]
Total revenues									1,767,222	2,007,333	1,948,376
Lease revenues
Disaggregation of Revenue [Line Items]
Lease income									1,719,710	1,953,412	1,894,333
Property rentals
Disaggregation of Revenue [Line Items]
Lease income									1,589,539	1,816,329	1,762,824
Hotel Pennsylvania
Disaggregation of Revenue [Line Items]
Lease income									89,594	94,399	89,302
Trade shows
Disaggregation of Revenue [Line Items]
Lease income									40,577	42,684	42,207
Tenant services
Disaggregation of Revenue [Line Items]
Revenues									47,512	53,921	54,043
Fee and other income
Disaggregation of Revenue [Line Items]
Revenues									157,478	156,387	135,750
Total revenues									157,478	156,387	135,750
BMS cleaning fees
Disaggregation of Revenue [Line Items]
Revenues									124,674	120,357	104,143
Management and leasing fees
Disaggregation of Revenue [Line Items]
Revenues									13,542	13,324	10,087
Other income
Disaggregation of Revenue [Line Items]
Revenues									19,262	22,706	21,520
New York
Disaggregation of Revenue [Line Items]
Total revenues									1,577,860	1,836,036	1,779,307
New York | Rental revenues
Disaggregation of Revenue [Line Items]
Total revenues									1,424,990	1,683,976	1,644,192
New York | Lease revenues
Disaggregation of Revenue [Line Items]
Lease income									1,389,979	1,642,625	1,601,919
New York | Property rentals
Disaggregation of Revenue [Line Items]
Lease income									1,300,385	1,548,226	1,512,617
New York | Hotel Pennsylvania
Disaggregation of Revenue [Line Items]
Lease income									89,594	94,399	89,302
New York | Trade shows
Disaggregation of Revenue [Line Items]
Lease income									0	0	0
New York | Tenant services
Disaggregation of Revenue [Line Items]
Revenues									35,011	41,351	42,273
New York | Fee and other income
Disaggregation of Revenue [Line Items]
Revenues									152,870	152,060	135,115
New York | BMS cleaning fees
Disaggregation of Revenue [Line Items]
Revenues									133,358	129,088	110,986
New York | Management and leasing fees
Disaggregation of Revenue [Line Items]
Revenues									13,694	12,203	8,599
New York | Other income
Disaggregation of Revenue [Line Items]
Revenues									5,818	10,769	15,530
Other
Disaggregation of Revenue [Line Items]
Total revenues									346,840	327,684	304,819
Other | Rental revenues
Disaggregation of Revenue [Line Items]
Total revenues									342,232	323,357	304,184
Other | Lease revenues
Disaggregation of Revenue [Line Items]
Lease income									329,731	310,787	292,414
Other | Property rentals
Disaggregation of Revenue [Line Items]
Lease income									289,154	268,103	250,207
Other | Hotel Pennsylvania
Disaggregation of Revenue [Line Items]
Lease income									0	0	0
Other | Trade shows
Disaggregation of Revenue [Line Items]
Lease income									40,577	42,684	42,207
Other | Tenant services
Disaggregation of Revenue [Line Items]
Revenues									12,501	12,570	11,770
Other | Fee and other income
Disaggregation of Revenue [Line Items]
Revenues									4,608	4,327	635
Other | BMS cleaning fees
Disaggregation of Revenue [Line Items]
Revenues									(8,684)	(8,731)	(6,843)
Other | Management and leasing fees
Disaggregation of Revenue [Line Items]
Revenues									(152)	1,121	1,488
Other | Other income
Disaggregation of Revenue [Line Items]
Revenues									$ 13,444	$ 11,937	$ 5,990