Revenue Recognition - Revenues by Segment (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Disaggregation of Revenue [Line Items]
Lease income	$ 308,316	$ 409,232	$ 699,534	$ 896,538
Total revenues	343,026	463,103	787,558	997,771
Write-off of lease receivables deemed uncollectible			38,631	15,382
New York
Disaggregation of Revenue [Line Items]
Total revenues	270,628	376,381	626,243	819,666
Other
Disaggregation of Revenue [Line Items]
Total revenues	72,398	86,722	161,315	178,105
Property rentals
Disaggregation of Revenue [Line Items]
Lease income	308,316	372,160	679,490	829,901
Write-off of lease receivables deemed uncollectible	37,587	14,492	38,631	15,382
Property rentals | New York
Disaggregation of Revenue [Line Items]
Lease income	241,308	300,925	539,920	686,728
Property rentals | Other
Disaggregation of Revenue [Line Items]
Lease income	67,008	71,235	139,570	143,173
Hotel Pennsylvania
Disaggregation of Revenue [Line Items]
Lease income	0	25,525	8,741	38,134
Hotel Pennsylvania | New York
Disaggregation of Revenue [Line Items]
Lease income	0	25,525	8,741	38,134
Hotel Pennsylvania | Other
Disaggregation of Revenue [Line Items]
Lease income	0	0	0	0
Trade shows
Disaggregation of Revenue [Line Items]
Lease income	0	11,547	11,303	28,503
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	0	11,547	11,303	28,503
Lease revenues
Disaggregation of Revenue [Line Items]
Lease income	308,316	409,232	699,534	896,538
Lease revenues | New York
Disaggregation of Revenue [Line Items]
Lease income	241,308	326,450	548,661	724,862
Lease revenues | Other
Disaggregation of Revenue [Line Items]
Lease income	67,008	82,782	150,873	171,676
Tenant services
Disaggregation of Revenue [Line Items]
Revenue	6,878	12,067	16,934	24,638
Tenant services | New York
Disaggregation of Revenue [Line Items]
Revenue	4,341	9,337	11,721	18,562
Tenant services | Other
Disaggregation of Revenue [Line Items]
Revenue	2,537	2,730	5,213	6,076
Rental revenues
Disaggregation of Revenue [Line Items]
Total revenues	315,194	421,299	716,468	921,176
Rental revenues | New York
Disaggregation of Revenue [Line Items]
Total revenues	245,649	335,787	560,382	743,424
Rental revenues | Other
Disaggregation of Revenue [Line Items]
Total revenues	69,545	85,512	156,086	177,752
BMS cleaning fees
Disaggregation of Revenue [Line Items]
Revenue	21,115	32,570	53,581	62,355
BMS cleaning fees | New York
Disaggregation of Revenue [Line Items]
Revenue	22,405	34,944	56,834	66,701
BMS cleaning fees | Other
Disaggregation of Revenue [Line Items]
Revenue	(1,290)	(2,374)	(3,253)	(4,346)
Management and leasing fees
Disaggregation of Revenue [Line Items]
Revenue	1,837	4,500	4,704	6,737
Management and leasing fees | New York
Disaggregation of Revenue [Line Items]
Revenue	1,701	4,472	4,575	6,723
Management and leasing fees | Other
Disaggregation of Revenue [Line Items]
Revenue	136	28	129	14
Other income
Disaggregation of Revenue [Line Items]
Revenue	4,880	4,734	12,805	7,503
Other income | New York
Disaggregation of Revenue [Line Items]
Revenue	873	1,178	4,452	2,818
Other income | Other
Disaggregation of Revenue [Line Items]
Revenue	4,007	3,556	8,353	4,685
Fee and other income
Disaggregation of Revenue [Line Items]
Revenue	27,832	41,804	71,090	76,595
Total revenues	27,832	41,804	71,090	76,595
Fee and other income | New York
Disaggregation of Revenue [Line Items]
Revenue	24,979	40,594	65,861	76,242
Fee and other income | Other
Disaggregation of Revenue [Line Items]
Revenue	$ 2,853	$ 1,210	$ 5,229	$ 353