v3.19.3

INDEBTEDNESS - Convertible Senior Notes Narrative (Details) $ / shares in Units, shares in Millions |  |  |  | 9 Months Ended | 12 Months Ended
--- | --- | --- | --- | --- | ---
Dec. 31, 2018 USD ($) | May 25, 2018 USD ($) day $ / shares | Mar. 06, 2017 USD ($) day $ / shares | Sep. 30, 2019 USD ($) | Sep. 30, 2018 USD ($) | Dec. 31, 2018 USD ($) shares
Debt Instrument [Line Items] |  |  |  |  |  |
Principal payment on conversion of senior notes |  |  |  | $ 0 | $ 70,047,000 |
Loss on extinguishment of long-term debt |  |  |  | 0 | $ 1,625,000 |
Convertible Debt |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |
Conversion price (in USD per share) | $ / shares |  | $ 77.85 | $ 22.95 |  |  |
Carrying amount of equity component | $ 194,392,000 |  |  | 194,392,000 |  | $ 194,392,000
Issuance costs attributable to the liability component | 8,040,000 |  |  | 6,025,000 |  | 8,040,000
Convertible Debt | 2023 Notes |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |
Aggregate principal amount |  | $ 862,500,000 |  |  |  |
Interest rate |  | 0.50% |  |  |  |
Conversion rate |  | 0.0128456 |  |  |  |
Conversion price (in USD per share) | $ / shares |  | $ 77.85 |  |  |  |
Carrying amount of equity component | 154,019,000 | $ 155,300,000 |  | $ 154,019,000 |  | 154,019,000
Effective interest rate of the liability component |  | 4.69% |  | 4.69% |  |
Discounts and commissions payable |  | $ 6,000,000.0 |  |  |  |
Third party offering costs |  | 800,000 |  |  |  |
Issuance costs attributable to the liability component | 5,054,000 | $ 5,600,000 |  | $ 3,647,000 |  | 5,054,000
Convertible Debt | 2023 Notes | Debt Instrument, Conversion Term One |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |
Threshold trading days | day |  | 20 |  |  |  |
Threshold consecutive trading days | day |  | 30 |  |  |  |
Threshold percentage of stock price trigger |  | 130.00% |  |  |  |
Convertible Debt | 2023 Notes | Debt Instrument Conversion Term Two |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |
Threshold trading days | day |  | 5 |  |  |  |
Threshold consecutive trading days | day |  | 5 |  |  |  |
Threshold percentage of stock price trigger |  | 98.00% |  |  |  |
Convertible Debt | 2022 Notes |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |
Aggregate principal amount |  |  | $ 440,000,000.0 |  |  |
Interest rate |  |  | 0.375% |  |  |
Conversion rate |  |  | 0.0435749 |  |  |
Conversion price (in USD per share) | $ / shares |  |  | $ 22.95 |  |  |
Carrying amount of equity component | 40,373,000 |  | $ 86,200,000 | $ 40,373,000 |  | 40,373,000
Effective interest rate of the liability component |  |  | 5.34% | 5.34% |  |
Discounts and commissions payable |  |  | $ 11,000,000.0 |  |  |
Third party offering costs |  |  | 800,000 |  |  |
Issuance costs attributable to the liability component | 2,986,000 |  | $ 9,400,000 | $ 2,378,000 |  | 2,986,000
Notes converted |  |  |  |  |  | 228,300,000
Principal payment on conversion of senior notes |  |  |  |  |  | $ 219,400,000
Shares issued upon conversion (in shares) | shares |  |  |  |  |  | 7.3
Loss on extinguishment of long-term debt | 5,000,000.0 |  |  |  |  |
Reduction to additional paid in capital | $ 21,000,000.0 |  |  |  |  |
Convertible Debt | 2022 Notes | Debt Instrument, Conversion Term One |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |
Threshold trading days | day |  |  | 20 |  |  |
Threshold consecutive trading days | day |  |  | 30 |  |  |
Threshold percentage of stock price trigger |  |  | 130.00% |  |  |
Convertible Debt | 2022 Notes | Debt Instrument Conversion Term Two |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |
Threshold trading days | day |  |  | 5 |  |  |
Threshold consecutive trading days | day |  |  | 5 |  |  |
Threshold percentage of stock price trigger |  |  | 98.00% |  |  |

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