Real Estate - Summary of Acquisition (Parenthetical) (Detail) ft² in Thousands	3 Months Ended
	Mar. 31, 2019 ft² a Property	Mar. 31, 2018 ft² a Property
Business Acquisition [Line Items]
Number of operating properties	12	0
Square feet | ft²	967	0
Operating Properties [Member]
Business Acquisition [Line Items]
Number of operating properties		0
Acquisitions of Properties from Third Parties [Member] | Land [Member]
Business Acquisition [Line Items]
Square feet | a	188	379