Organization (Detail) ft² in Millions	Jun. 30, 2017 ft² property
Real Estate Properties [Line Items]
Number of real estate properties | property	139
Area of real estate property (square feet) | ft²	16.2
Number of real estate properties additionally managed | property	19
Area of real estate property additionally managed | ft²	1.2
Maximum
Real Estate Properties [Line Items]
Ownership Interest	100.00%