Debt - Convertible Notes - Narrative (Details) - Convertible Senior Notes |
1 Months Ended | ||
|---|---|---|---|
|
May 31, 2014
USD ($)
$ / shares
|
Jun. 30, 2018
USD ($)
|
Dec. 31, 2017
USD ($)
|
|
| Debt Instrument [Line Items] | |||
| Conversion rate | 0.0763636 | 0.087013 | |
| Conversion price (in USD per share) | $ / shares | $ 13.10 | ||
| Premium above public offering price | 22.50% | ||
| Anti-dilutive cash dividends, exceeding (in USD per share) | $ / shares | $ 0.16625 | ||
| Debt discount, value of the embedded conversion premium | $ 56,700,000 | $ 18,600,000 | $ 23,700,000 |
| Unamortized deferred financing costs | 19,600,000 | $ 6,200,000 | $ 8,000,000 |
| Convertible Senior Notes Due 2019 | |||
| Debt Instrument [Line Items] | |||
| Aggregate principal amount of debt | $ 402,500,000.0 | ||
| Stated interest rate | 2.875% | ||
| Convertible Senior Notes Due 2021 | |||
| Debt Instrument [Line Items] | |||
| Aggregate principal amount of debt | $ 345,000,000.0 | ||
| Stated interest rate | 3.75% |