Long-Term Debt - Convertible Debt (Details) - USD ($) |
Dec. 31, 2016 |
Dec. 31, 2015 |
|---|---|---|
| Debt Instrument [Line Items] | ||
| Long-term debt | $ 161,349,000 | $ 47,120,000 |
| Convertible senior subordinated debentures at 4.125%, due in February 2027 | Convertible Subordinated Debt | ||
| Debt Disclosure [Abstract] | ||
| Initial conversion price | $ 24.79 | |
| Debt Instrument [Line Items] | ||
| Interest rate (as a percent) | 4.125% | |
| Carrying amount of equity component | $ 25,381,000 | 25,381,000 |
| Principal amount of liability component | 13,350,000 | 13,350,000 |
| Unamortized discount | (311,000) | (1,203,000) |
| Long-term debt | $ 13,039,000 | $ 12,147,000 |