Real Estate - Summary of Acquisition (Detail) ft² in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018 USD ($) ft² Property	Sep. 30, 2017 USD ($) ft² Property	Sep. 30, 2018 USD ($) ft² Property	Sep. 30, 2017 USD ($) ft² Property
Real Estate [Abstract]
Number of operating properties | Property	5	12	8	14
Square feet | ft²	523	6,328	1,406	6,478
Acquisition value of net investments in real estate properties | $	$ 183,484	$ 703,686	$ 497,783	$ 744,581