Unconsolidated Investments - Summarized Operating Results of Unconsolidated Investees (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Equity Method Investments and Joint Ventures [Abstract]
Revenue	$ 70,156	$ 82,744	$ 179,689	$ 183,103
Cost of revenue	29,829	28,149	60,166	57,738
Operating expenses	34,589	919	53,743	1,633
Other expense	18,833	15,135	39,684	37,976
Net income (loss)	$ (13,095)	$ 38,541	$ 26,096	$ 85,756