Debt - Schedule of Total Interest Expense on Convertible Senior Notes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Debt Instrument [Line Items]
Amortization of debt issuance costs (Non-cash)	$ 1,133	$ 1,059	$ 1,099
Accretion of debt discount (Non-cash)	3,866	3,594	2,826
2019 Notes [Member]
Debt Instrument [Line Items]
Contractual interest expense (Cash)	8,553	8,553	6,795
Amortization of debt issuance costs (Non-cash)	989	920	684
Accretion of debt discount (Non-cash)	3,866	3,594	2,674
Total interest expense	$ 13,408	$ 13,067	$ 10,153
Effective interest rate of the liability component	7.32%	7.32%	7.32%
Quoted prices in active markets using identical assets (Level 1) [Member] | 2019 Notes [Member]
Debt Instrument [Line Items]
Fair value of debt instrument	$ 167,800