Equity - Summary of Class A Common Stock Issuances (Detail) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended				12 Months Ended
	Jun. 30, 2015	May 31, 2015	Apr. 30, 2015	May 31, 2013	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Class of Stock [Line Items]
Shares issued				25,875,000	1,070	34,780,622	28,275,006
Net proceeds					$ 27	$ 1,029,540	$ 766,138
Class A Common Stock [Member]
Class of Stock [Line Items]
Shares issued	11,500,000	280,025	23,000,000		0	34,780,025
Share issue price	$ 29.42	$ 29.97	$ 29.75			$ 29.64
Net proceeds	$ 337,918	$ 7,895	$ 683,722			$ 1,029,535