Real Estate - Summary of Acquisition (Parenthetical) (Detail) ft² in Thousands	Dec. 31, 2016 ft² a	Dec. 31, 2015 ft² a	Dec. 31, 2014 ft² a
Land [Member]
Business Acquisition [Line Items]
Square Feet	5,892	7,404
Acquisitions of Properties from Third Parties [Member]
Business Acquisition [Line Items]
Square Feet | ft²	1,823	7,375	1,004
Acquisitions of Properties from Third Parties [Member] | Land [Member]
Business Acquisition [Line Items]
Square Feet	776	690	1,040