Operating Leases - Additional Information (Details)	12 Months Ended
	Dec. 31, 2017
Commercial Tenant Lease | Minimum
Property Subject to or Available for Operating Lease [Line Items]
Lease term	5 years
Commercial Tenant Lease | Maximum
Property Subject to or Available for Operating Lease [Line Items]
Lease term	20 years
Multifamily residential real estate | Minimum
Property Subject to or Available for Operating Lease [Line Items]
Lease term	7 months
Multifamily residential real estate | Maximum
Property Subject to or Available for Operating Lease [Line Items]
Lease term	15 months
Multifamily residential real estate | Majority
Property Subject to or Available for Operating Lease [Line Items]
Lease term	12 months
Apartment Leases | Maximum
Property Subject to or Available for Operating Lease [Line Items]
Lease term	1 year