Summary of Significant Accounting Policies - Estimated Useful Lives of Real Estate Investments (Detail)	9 Months Ended
	Sep. 30, 2017
Minimum | Buildings and building improvements
Property Subject to or Available for Operating Lease [Line Items]
Estimated useful lives	20 years
Minimum | Land improvements
Property Subject to or Available for Operating Lease [Line Items]
Estimated useful lives	10 years
Minimum | Fixtures and integral equipment
Property Subject to or Available for Operating Lease [Line Items]
Estimated useful lives	3 years
Maximum | Buildings and building improvements
Property Subject to or Available for Operating Lease [Line Items]
Estimated useful lives	40 years
Maximum | Land improvements
Property Subject to or Available for Operating Lease [Line Items]
Estimated useful lives	20 years
Maximum | Fixtures and integral equipment
Property Subject to or Available for Operating Lease [Line Items]
Estimated useful lives	20 years