Commitments and Contingencies - Narrative (Details)	6 Months Ended
	Jun. 30, 2018 USD ($)
Real Estate Properties [Line Items]
General liability insurance limit	$ 200,000,000
Property and rental value insurance coverage limit	2,000,000,000.0
Terrorist acts insurance coverage limit	2,000,000,000
Purchase obligation	461,000,000
Additional capital funding committed amount	48,600,000
Consolidated Properties
Real Estate Properties [Line Items]
Purchase obligation	362,900,000
Principal payment guarantees	61,300,000
Unconsolidated Properties
Real Estate Properties [Line Items]
Purchase obligation	98,100,000
Principal payment guarantees	$ 0
Minimum
Real Estate Properties [Line Items]
Commitment amortization period	2 years
Minimum | Unconsolidated Properties
Real Estate Properties [Line Items]
Commitment amortization period	2 years
Maximum
Real Estate Properties [Line Items]
Commitment amortization period	3 years
Maximum | Unconsolidated Properties
Real Estate Properties [Line Items]
Commitment amortization period	3 years