Long-term Debt - Total Interest Expense Recognized Related to Convertible Notes(Details) - Senior Notes - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Schedule Of Interest Expenses [Line Items]
Contractual interest expense	$ 1,812	$ 1,813	$ 5,438	$ 5,438
Amortization of debt discount	2,264	2,058	6,634	6,032
Amortization of debt issuance cost	41	36	116	105
Total interest expense	$ 4,117	$ 3,907	$ 12,188	$ 11,575