Debt - Interest Expense (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Jul. 31, 2020
Long-term debt
Amortization of debt issuance costs	$ 1,020	$ 694	$ 524
Effective interest rate of the liability component	10.40%			11.00%
Convertible debt \| 3.00% Convertible senior notes due 2022
Long-term debt
Contractual interest expense	$ 4,500	4,500
Amortization of debt issuance costs	464	417
Amortization of debt discount	9,314	8,368
Total	$ 14,278	$ 13,285
Effective interest rate of the liability component	11.00%	11.00%
Convertible debt \| 1.50% Convertible senior notes due 2026
Long-term debt
Contractual interest expense	$ 4,319	$ 1,220
Amortization of debt issuance costs	508	140
Amortization of debt discount	13,285	3,659
Total	$ 18,112	$ 5,019
Effective interest rate of the liability component	10.20%	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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