Other Income (Loss), Net - Schedule of Other Income (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Other Income and Expenses [Abstract]
Gain (loss) on sales/distributions of ownership interests	$ 192	$ 2,842	$ 3,846	$ 2,888
Total other income (loss), net	$ 192	$ 2,842	$ 3,846	$ 2,888