Fair Value Measurements - Additional Information (Details) - USD ($) |
Sep. 30, 2016 |
Dec. 31, 2015 |
Jun. 30, 2014 |
|---|---|---|---|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | |||
| Unamortized discount | $ 73,148,000 | $ 25,704,000 | |
| 2% Convertible Senior Notes | |||
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | |||
| Principal amount of Senior Notes | $ 201,300,000.0 | ||
| Debt, interest rate | 2.00% | 2.00% |