Convertible Senior Notes - Schedule of Convertible Notes (Details) - Convertible Debt - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Convertible Senior Notes Due February 2023
Liability component:
Principal	$ 229,997	$ 229,999
Unamortized debt discount	(30,942)	(33,376)
Unamortized debt issuance costs	(3,228)	(3,486)
Net carrying amount	195,827	193,137
Convertible Senior Notes Due February 2023 \| Additional Paid-In Capital
Equity component:
Net carrying amount	48,919	48,919
Convertible Senior Notes Due June 2026
Liability component:
Principal	316,250	316,250
Unamortized debt discount	(76,073)	(78,672)
Unamortized debt issuance costs	(5,732)	(5,931)
Net carrying amount	234,445	231,647
Convertible Senior Notes Due June 2026 \| Additional Paid-In Capital
Equity component:
Net carrying amount	$ 81,550	$ 81,550

Debt Instrument, Convertible, Carrying Amount of Equity Component, Net

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Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

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Amount, after accumulated amortization, of debt discount (premium).

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The remaining balance of debt issuance expenses that were capitalized and are being amortized against income over the lives of the respective bond issues. This does not include the amounts capitalized as part of the cost of the utility plant or asset.

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