Revenue Recognition - Revenues by Segment (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Disaggregation of Revenue [Line Items]
Lease income	$ 409,232		$ 896,538
Total revenues	463,103	$ 541,818	997,771	$ 1,078,255
New York
Disaggregation of Revenue [Line Items]
Total revenues	376,381	458,552	819,666	907,036
Other
Disaggregation of Revenue [Line Items]
Total revenues	86,722	83,266	178,105	171,219
Rental revenues
Disaggregation of Revenue [Line Items]
Total revenues	421,299	502,907	921,176	1,003,327
Rental revenues | New York
Disaggregation of Revenue [Line Items]
Total revenues	335,787	420,916	743,424	834,752
Rental revenues | Other
Disaggregation of Revenue [Line Items]
Total revenues	85,512	81,991	177,752	168,575
Property rentals(1)(2)
Disaggregation of Revenue [Line Items]
Lease income	372,160	450,711	829,901	905,142
Write-offs of lease receivables	14,492		15,382
Lease termination income	2,499		2,499
Property rentals(1)(2) | New York
Disaggregation of Revenue [Line Items]
Lease income	300,925	383,440	686,728	772,840
Property rentals(1)(2) | Other
Disaggregation of Revenue [Line Items]
Lease income	71,235	67,271	143,173	132,302
Hotel Pennsylvania
Disaggregation of Revenue [Line Items]
Lease income	25,525	27,082	38,134	41,754
Hotel Pennsylvania | New York
Disaggregation of Revenue [Line Items]
Lease income	25,525	27,082	38,134	41,754
Hotel Pennsylvania | Other
Disaggregation of Revenue [Line Items]
Lease income	0	0	0	0
Trade shows
Disaggregation of Revenue [Line Items]
Lease income	11,547	11,586	28,503	30,461
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	11,547	11,586	28,503	30,461
Lease revenues
Disaggregation of Revenue [Line Items]
Lease income	409,232	489,379	896,538	977,357
Lease revenues | New York
Disaggregation of Revenue [Line Items]
Lease income	326,450	410,522	724,862	814,594
Lease revenues | Other
Disaggregation of Revenue [Line Items]
Lease income	82,782	78,857	171,676	162,763
Tenant services
Disaggregation of Revenue [Line Items]
Revenue	12,067	13,528	24,638	25,970
Tenant services | New York
Disaggregation of Revenue [Line Items]
Revenue	9,337	10,394	18,562	20,158
Tenant services | Other
Disaggregation of Revenue [Line Items]
Revenue	2,730	3,134	6,076	5,812
Fee and other income
Disaggregation of Revenue [Line Items]
Revenue	41,804	38,911	76,595	74,928
Total revenues	41,804	38,911	76,595	74,928
Fee and other income | New York
Disaggregation of Revenue [Line Items]
Revenue	40,594	37,636	76,242	72,284
Fee and other income | Other
Disaggregation of Revenue [Line Items]
Revenue		1,275	353	2,644
Lease termination income	1,210
BMS cleaning fees
Disaggregation of Revenue [Line Items]
Revenue	32,570	30,867	62,355	59,222
BMS cleaning fees | New York
Disaggregation of Revenue [Line Items]
Revenue	34,944	33,407	66,701	63,560
BMS cleaning fees | Other
Disaggregation of Revenue [Line Items]
Revenue	(2,374)	(2,540)	(4,346)	(4,338)
Management and leasing fees
Disaggregation of Revenue [Line Items]
Revenue	4,500	2,707	6,737	5,471
Management and leasing fees | New York
Disaggregation of Revenue [Line Items]
Revenue	4,472	2,464	6,723	4,945
Management and leasing fees | Other
Disaggregation of Revenue [Line Items]
Revenue	28	243	14	526
Other income
Disaggregation of Revenue [Line Items]
Revenue	4,734	5,337	7,503	10,235
Lease termination income		804		1,149
Other income | New York
Disaggregation of Revenue [Line Items]
Revenue	1,178	1,765	2,818	3,779
Other income | Other
Disaggregation of Revenue [Line Items]
Revenue	$ 3,556	$ 3,572	$ 4,685	$ 6,456