Organization - Additional Information (Detail)	Sep. 30, 2020 property
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of properties in greater New York City metropolitan area (property)	7

The number of real estate properties owned as of the balance sheet date.

No definition available.

Name:	us-gaap_NumberOfRealEstateProperties
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant