Summary of Estimated Useful Lives of Assets (Detail)	6 Months Ended
	Jun. 30, 2017
Building | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful lives of assets	30 years
Building | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful lives of assets	40 years
Site Improvements | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful lives of assets	1 year
Site Improvements | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful lives of assets	28 years