Revenue Recognition - Revenues by Segment (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Disaggregation of Revenue [Line Items]
Lease income	$ 414,343		$ 1,310,881
Total revenues	465,961	$ 542,048	1,463,732	$ 1,620,303
New York
Disaggregation of Revenue [Line Items]
Total revenues	380,568	462,446	1,200,234	1,369,482
Other
Disaggregation of Revenue [Line Items]
Total revenues	85,393	79,602	263,498	250,821
Rental revenues
Disaggregation of Revenue [Line Items]
Total revenues	427,638	503,947	1,348,814	1,507,274
Rental revenues | New York
Disaggregation of Revenue [Line Items]
Total revenues	342,774	425,084	1,086,198	1,259,836
Rental revenues | Other
Disaggregation of Revenue [Line Items]
Total revenues	84,864	78,863	262,616	247,438
Property rentals
Disaggregation of Revenue [Line Items]
Lease income	381,740	453,789	1,211,641	1,358,932
Property rentals | New York
Disaggregation of Revenue [Line Items]
Lease income	308,933	387,300	995,661	1,160,140
Property rentals | Other
Disaggregation of Revenue [Line Items]
Lease income	72,807	66,489	215,980	198,792
Hotel Pennsylvania
Disaggregation of Revenue [Line Items]
Lease income	24,499	26,088	62,633	67,842
Hotel Pennsylvania | New York
Disaggregation of Revenue [Line Items]
Lease income	24,499	26,088	62,633	67,842
Hotel Pennsylvania | Other
Disaggregation of Revenue [Line Items]
Lease income	0	0	0	0
Trade shows
Disaggregation of Revenue [Line Items]
Lease income	8,104	8,443	36,607	38,903
Trade shows | New York
Disaggregation of Revenue [Line Items]
Lease income	0	0	0	0
Trade shows | Other
Disaggregation of Revenue [Line Items]
Lease income	8,104	8,443	36,607	38,903
Lease revenues
Disaggregation of Revenue [Line Items]
Lease income	414,343	488,320	1,310,881	1,465,677
Lease revenues | New York
Disaggregation of Revenue [Line Items]
Lease income	333,432	413,388	1,058,294	1,227,982
Lease revenues | Other
Disaggregation of Revenue [Line Items]
Lease income	80,911	74,932	252,587	237,695
Tenant services
Disaggregation of Revenue [Line Items]
Revenue	13,295	15,627	37,933	41,597
Tenant services | New York
Disaggregation of Revenue [Line Items]
Revenue	9,342	11,696	27,904	31,854
Tenant services | Other
Disaggregation of Revenue [Line Items]
Revenue	3,953	3,931	10,029	9,743
Fee and other income
Disaggregation of Revenue [Line Items]
Revenue	38,323	38,101	114,918	113,029
Total revenues	38,323	38,101	114,918	113,029
Fee and other income | New York
Disaggregation of Revenue [Line Items]
Revenue	37,794	37,362	114,036	109,646
Fee and other income | Other
Disaggregation of Revenue [Line Items]
Revenue	529	739	882	3,383
BMS cleaning fees
Disaggregation of Revenue [Line Items]
Revenue	30,677	28,873	93,032	88,095
BMS cleaning fees | New York
Disaggregation of Revenue [Line Items]
Revenue	32,787	31,328	99,488	94,888
BMS cleaning fees | Other
Disaggregation of Revenue [Line Items]
Revenue	(2,110)	(2,455)	(6,456)	(6,793)
Management and leasing fees
Disaggregation of Revenue [Line Items]
Revenue	3,326	4,734	10,063	10,205
Management and leasing fees | New York
Disaggregation of Revenue [Line Items]
Revenue	3,746	4,439	10,469	9,384
Management and leasing fees | Other
Disaggregation of Revenue [Line Items]
Revenue	(420)	295	(406)	821
Other income
Disaggregation of Revenue [Line Items]
Revenue	4,320	4,494	11,823	14,729
Other income | New York
Disaggregation of Revenue [Line Items]
Revenue	1,261	1,595	4,079	5,374
Other income | Other
Disaggregation of Revenue [Line Items]
Revenue	$ 3,059	$ 2,899	$ 7,744	$ 9,355