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Long-term Debt Senior Convertible Notes (Details) |  | 12 Months Ended
--- | --- | ---
Aug. 12, 2016 USD ($) $ / shares | Dec. 31, 2019 USD ($) $ / shares | Dec. 31, 2018 USD ($) | Dec. 31, 2017 USD ($)
Senior Convertible Notes [Line Items] |  |  |  |
Senior Convertible Notes, net carrying amount |  | $ 157,263,000 | $ 147,894,000 |
Capped call transaction costs | $ 24,200,000 |  |  |
Capped Call, Cap Price | $ / shares | $ 60.00 |  |  |
Capitalized interest costs |  | 18,500,000 | 20,600,000 | $ 12,600,000
1.50% Senior Convertible Notes Due 2021 [Member] |  |  |  |
Senior Convertible Notes [Line Items] |  |  |  |
Senior Convertible Notes, principal amount | $ 172,500,000 | $ 172,500,000 | 172,500,000 |
Senior Convertible Notes, interest rate, stated percentage |  | 1.50% |  |
Proceeds from Debt, Net of Issuance Costs | 166,600,000 |  |  |
Senior Convertible Notes, debt issuance costs | (5,900,000) |  |  |
Senior Convertible Notes, threshold trading days |  | 20 |  |
Senior Convertible Notes, threshold consecutive trading days |  | 30 |  |
Senior Convertible Notes, threshold percentage of stock price trigger |  | 130.00% |  |
Senior Convertible Notes, threshold business days, trading price trigger |  | 5 days |  |
Senior Convertible Notes, threshold trading days, trading price trigger |  | 5 days |  |
Senior Convertible Notes, principal amount of note |  | $ 1,000 |  |
Senior Convertible Notes, threshold percentage of trading price trigger |  | 98.00% |  |
Senior Convertible Notes, conversion rate |  | 24.6914 |  |
Senior Convertible Notes, conversion price | $ / shares |  | $ 40.50 |  |
Senior Convertible Notes, initial fair value of liability component | $ 132,300,000 |  |  |
Senior Convertible Notes, effective interest rate | 7.25% |  |  |
Senior Convertible Notes, initial value of equity component | $ 40,200,000 |  |  |
Senior Convertible Notes, interest expense |  | $ 11,000,000.0 | 10,500,000 | $ 9,900,000
Senior Convertible Notes, unamortized debt discount |  | (13,861,000) | (22,313,000) |
Unamortized deferred financing costs |  | (1,376,000) | (2,293,000) |
Senior Convertible Notes, net carrying amount |  | 157,263,000 | 147,894,000 |
Senior Convertible Notes, net carrying amount, equity component |  | $ 33,600,000 | $ 33,600,000 |

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