Leases - Lessor Narrative (Details)	Sep. 30, 2019
Minimum
Lessor, Lease, Description [Line Items]
Lessor, operating lease, term (years)	5 years
Maximum
Lessor, Lease, Description [Line Items]
Lessor, operating lease, term (years)	25 years
Alexander Apartment Tower | Minimum
Lessor, Lease, Description [Line Items]
Lessor, operating lease, term (years)	1 year
Alexander Apartment Tower | Maximum
Lessor, Lease, Description [Line Items]
Lessor, operating lease, term (years)	2 years