Equity - Schedule of Movement in Outstanding Shares of Class A Common Stock, Restricted Class A Common Stock and Deferred Stock Units (Detail) - shares	1 Months Ended	3 Months Ended
	May 31, 2013	Mar. 31, 2018	Mar. 31, 2017
Equity [Abstract]
Beginning balance		108,081,077	94,709,290
Issuance of class A common stock	25,875,000	455	270
Issuance of restricted class A common stock, net		309,775	277,815
Issuance of deferred stock units		7,871	6,415
Ending balance		108,399,178	94,993,790