Equity - Summary of Class A Common Stock Issuances (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	9 Months Ended		1 Months Ended			9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014 Class A Common Stock [Member]	Apr. 30, 2014 Class A Common Stock [Member]	Jan. 31, 2014 Class A Common Stock [Member]	Sep. 30, 2014 Class A Common Stock [Member]
Shares Issued	28,175,003	25,875,000	9,200,000	9,200,000	9,775,000	28,175,000
Net Proceeds	$ 763,407	$ 633,810	$ 252,555	$ 254,758	$ 256,092	$ 763,405
Issue Price			$ 27.49	$ 27.72	$ 26.25	$ 27.13