Debt - Mortgage Debt (Details) - Fixed rate mortgage debt - USD ($) $ in Thousands	Dec. 31, 2020	Nov. 30, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Fixed rate debt	$ 786,884		$ 610,821
250 West 57th Street
Debt Instrument [Line Items]
Fixed rate debt	$ 180,000	$ 180,000	$ 0
Stated interest rate (as a percent)	2.83%	2.83%

Contractual interest rate for funds borrowed, under the debt agreement.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant