Convertible Notes and Credit Facility - Components of Notes (Details) - Convertible Debt - USD ($) $ in Thousands |
Sep. 30, 2019 |
Dec. 31, 2018 |
Jun. 30, 2018 |
Mar. 31, 2018 |
Feb. 28, 2014 |
---|---|---|---|---|---|
Debt Instrument [Line Items] | |||||
Net carrying value of convertible notes | $ 49,853 | $ 172,058 | |||
2014 Notes | |||||
Debt Instrument [Line Items] | |||||
Interest rate on notes | 2.75% | 2.75% | |||
Principal amount | $ 51,250 | 51,250 | |||
Unamortized debt discount | (1,182) | (1,232) | $ (6,000) | ||
Unamortized debt issuance cost | (215) | (224) | |||
Net carrying value of convertible notes | $ 49,853 | 49,794 | |||
2018 Notes | |||||
Debt Instrument [Line Items] | |||||
Interest rate on notes | 2.75% | 2.75% | 2.75% | ||
Principal amount | $ 0 | 149,999 | $ 150,000 | ||
Premium accretion | 0 | 3,755 | |||
Unamortized debt discount | 0 | (29,558) | |||
Unamortized debt issuance cost | 0 | (1,932) | |||
Net carrying value of convertible notes | $ 0 | $ 122,264 |