Equity - Schedule of Details Movement in Our Outstanding Class A Common Stock and Restricted Class A Common Stock (Detail)	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
Equity [Abstract]
Beginning balance	3,016,407	2,277,344
Issuance of class A common stock	25,875,000
Issuance of restricted class A common stock, net		36,400
Issuance of deferred stock units	6,758	5,418
Ending balance	28,898,165	2,319,162