Financial Instruments and Fair Value Measurements - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2020	Dec. 31, 2019
Fair Value Measurements
Liabilities at fair value	$ 0
Transfers between level 1 and level 2, assets	0
Transfers between level 2 and level 1, assets	0
Transfers between level 1 and level 2, liabilities	0
Transfers between level 2 and level 1, liabilities	0
Transfer of assets into level 3	0
Transfer of assets out of level 3	0
Transfer of liabilities into level 3	0
Transfer of liabilities out of level 3	0
Convertible senior notes	524,905	$ 644,751
Convertible Senior Unsecured Notes 2021 Notes
Fair Value Measurements
Convertible senior notes	96,500
Convertible Senior Unsecured Notes 2021 Notes \| Fair Value, Inputs, Level 2
Fair Value Measurements
Convertible senior notes, fair value	87,200
Convertible Senior Unsecured Notes 2024 Notes
Fair Value Measurements
Convertible senior notes	135,100
Convertible senior notes, fair value	145,500
Convertible Senior Unsecured Notes 2025 Notes
Fair Value Measurements
Convertible senior notes	293,300
Convertible senior notes, fair value	$ 185,100

Carrying amount of long-term convertible debt as of the balance sheet date, net of the amount due in the next twelve months or greater than the normal operating cycle, if longer. The debt is convertible into another form of financial instrument, typically the entity's common stock.

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Fair value portion of debt instrument payable, including, but not limited to, notes payable and loans payable.

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-Publisher FASB
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Amount of transfers of assets measured on a recurring basis out of Level 1 of the fair value hierarchy into Level 2.

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Fair value of financial and nonfinancial obligations.

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