Interest Expense Related to Convertible Notes (Detail) - Senior Notes - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Schedule Of Interest Expenses [Line Items]
Contractual interest expense	$ 7,250	$ 3,887
Amortization of debt discount	8,141	4,058
Amortization of debt issuance cost	142	71
Total interest expense	$ 15,533	$ 8,016