Deferred Costs, Acquired Lease Intangibles and Goodwill - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Jun. 30, 2020	Dec. 31, 2019
Deferred Costs [Line Items]
Amortization expense related to deferred leasing costs	$ 5,400	$ 6,200	$ 17,700	$ 18,300
Rental revenue related to amortization of below-market leases, net of above-market leases	700	1,700	2,953	5,780
Goodwill	491,479		491,479			$ 491,479
Lease agreements
Deferred Costs [Line Items]
Amortization expense related to acquired lease intangibles	1,500	$ 2,400	5,900	$ 8,200
Observatory
Deferred Costs [Line Items]
Goodwill	227,500		227,500
Real estate
Deferred Costs [Line Items]
Goodwill	264,000		264,000
Revolving credit facility | Unsecured revolving credit facility
Deferred Costs [Line Items]
Net deferred financing costs	$ 2,700		$ 2,700			$ 4,200
Observatory
Deferred Costs [Line Items]
Fair value in excess of carrying value (less than) (as a percent)					5.00%