Real Estate - Investments in Real Estate Properties (Parenthetical) (Detail) $ in Thousands	6 Months Ended
	Jun. 30, 2018 USD ($) a Property	Jun. 30, 2017 USD ($)	Dec. 31, 2017 a
Real Estate Properties [Line Items]
Number of operating properties acquired | Property	3
Acquisition value of operating properties	$ 33,289	$ 37,253
Real Estate Operating Property [Member]
Real Estate Properties [Line Items]
Acquisition value of operating properties	$ 103,100
Land [Member]
Real Estate Properties [Line Items]
Acquisition of net investments in real estate properties, square feet | a	808
Acquisition value of net investments in real estate properties	$ 211,200
Square Feet | a	5,220		5,191