Unconsolidated Investments - Summarized Operating Results of Unconsolidated Investees (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Equity Method Investments and Joint Ventures [Abstract]
Revenue	$ 65,026	$ 45,008	$ 244,715	$ 228,111
Cost of revenue	29,017	31,550	89,183	89,288
Operating expenses	20,490	11,030	74,233	12,663
Other expense	17,434	12,062	57,118	50,038
Net income (loss)	$ (1,915)	$ (9,634)	$ 24,181	$ 76,122