Long-Term Debt - Accretion of Debt Discount and Amortization of Financing Costs (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Debt Instrument [Line Items]
Contractual coupon interest		$ 1,527	$ 4,237	$ 2,712
Accretion of debt discount		3,621	7,146	6,836
Amortization of deferred financing costs		364	649	711
Total		5,512	12,032	10,259
Convertible Debt \| Convertible Notes 2024
Debt Instrument [Line Items]
Contractual coupon interest	$ 2,000	600	4,000	600
Accretion of debt discount	3,255	1,101	6,477	1,101
Amortization of deferred financing costs	291	98	579	98
Total	$ 5,546	1,799	11,056	1,799
Convertible Debt \| Convertible Notes 2020
Debt Instrument [Line Items]
Contractual coupon interest		927	237	2,112
Accretion of debt discount		2,520	669	5,735
Amortization of deferred financing costs		266	70	613
Total		$ 3,713	$ 976	$ 8,460

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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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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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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