Long-term Debt - Interest Expense on Note (Details) - Senior notes - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020
2025 Notes
Debt Instrument [Line Items]
Coupon interest	$ 719	$ 0
Amortization of debt discount	2,179	0
Amortization of debt issuance costs	287	0
Total interest expense recognized	3,185	0
2023 Notes
Debt Instrument [Line Items]
Coupon interest	30	854
Amortization of debt discount	37	977
Amortization of debt issuance costs	7	206
Total interest expense recognized	$ 74	$ 2,037

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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