Foreign Currency Translation - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Foreign Currency [Abstract]
Gain (loss) on foreign currency translation	$ (3,071)	$ 1,287	$ 10,076
Foreign currency translation gain (loss)	$ 19,632	$ (7,545)	$ (36,004)