Debt - Interest Expense (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Jul. 17, 2020
Long-term debt
Amortization of debt issuance costs			$ 1,377	$ 766
Effective interest rate of the liability component	11.00%		11.00%		11.00%
Convertible debt \| 3.00% Convertible senior notes due 2022
Long-term debt
Contractual interest expense	$ 1,134	$ 1,131	$ 3,375	3,375
Amortization of debt issuance costs	182	118	538	343
Amortization of debt discount		2,372		6,892
Total	$ 1,316	$ 3,621	$ 3,913	$ 10,610
Effective interest rate of the liability component	3.50%	11.00%	3.50%	11.00%
Convertible debt \| 1.50% Convertible senior notes due 2026
Long-term debt
Contractual interest expense	$ 1,081	$ 1,081	$ 3,217	$ 3,223
Amortization of debt issuance costs	283	127	839	374
Amortization of debt discount		3,313		9,786
Total	$ 1,364	$ 4,521	$ 4,056	$ 13,383
Effective interest rate of the liability component	1.90%	10.20%	1.90%	10.20%

Amount of noncash expense included in interest expense to amortize debt discount and premium associated with the related debt instruments. Excludes amortization of financing costs. Alternate captions include noncash interest expense.

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Amount of amortization expense attributable to debt issuance costs.

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Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

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Amount of the cost of borrowed funds accounted for as interest expense for debt.

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Represents the portion of interest incurred in the period on debt arrangements that was charged against earnings, excluding amortization of debt discount (premium) and financing costs.

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