Equity - Summary of Class A Common Stock Issuances (Detail) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended			6 Months Ended
	Jun. 30, 2015	May. 31, 2015	Apr. 30, 2015	Jun. 30, 2015	Jun. 30, 2014
Shares issued		280,025		34,780,298	18,975,001
Net proceeds		$ 7,900		$ 1,029,557	$ 510,845
Class A Common Stock [Member]
Shares issued	11,500,000	280,025	23,000,000	34,780,025
Share issue price	$ 29.42	$ 29.97	$ 29.75	$ 29.64
Net proceeds	$ 337,935	$ 7,895	$ 683,727	$ 1,029,557