Summary of Interest Expense on Convertible Debt (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Schedule Of Interest Expenses [Line Items]
Total interest expense on convertible debt	$ 38,244	$ 36,642	$ 10,447
Convertible Senior Notes
Schedule Of Interest Expenses [Line Items]
Coupon interest	9,750	9,417	4,550
Amortization of issuance costs	3,294	3,332	1,053
Accretion of debt discount	25,200	23,893	4,821
Total interest expense on convertible debt	$ 38,244	$ 36,642	$ 10,424