Long-term Debt - Interest Expense Related to Convertible Notes (Detail) - Convertible notes - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Schedule Of Interest Expenses [Line Items]
Contractual interest expense	$ 1,813	$ 1,813	$ 3,626	$ 3,625
Amortization of debt discount	2,211	1,965	4,370	3,973
Amortization of debt issuance cost	38	35	75	70
Total interest expense	$ 4,062	$ 3,813	$ 8,071	$ 7,668