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	6 Months Ended
	May 31, 2013	Jun. 30, 2018	Jun. 30, 2017
Equity [Abstract]
Beginning balance		108,081,077	94,709,290
Issuance of class A common stock	25,875,000	3,252,325	543
Issuance of restricted class A common stock, net		305,703	286,773
Issuance of deferred stock units		15,919	12,904
Ending balance		111,655,024	95,009,510