Fair Value - Schedule of Changes in Level 3 Future Purchase Rights Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Future Purchase Rights Liabilities [Roll Forward]
Re-measurement of future purchase rights	$ 0	$ (2,600)	$ 1,306
Fair Value, Measurements, Recurring [Member] | Level 3 [Member]
Future Purchase Rights Liabilities [Roll Forward]
Beginning balance	$ 0	2,600	0
Initial valuation of additional future purchase rights			1,294
Re-measurement of future purchase rights		2,600	(1,306)
Ending balance		$ 0	$ 2,600