Convertible Notes Interest Expense for December 2024 Notes (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019
Debt Instrument [Line Items]
Debt Instrument, Convertible, Beneficial Conversion Feature	$ 234	$ 1,766
Accreted interest on convertible note principal	33	0
Amortization of convertible notes conversion option and debt issuance costs	280	1,923
December 2024 Notes [Member]
Debt Instrument [Line Items]
Interest Expense, Debt	97	0
Debt Instrument, Convertible, Beneficial Conversion Feature	23	0
Contractual coupon interest	37	0
Accreted interest on convertible note principal	33	0
Amortization of convertible notes conversion option and debt issuance costs	$ 4	$ 0

Amount recognized for the passage of time, typically for liabilities, that have been discounted to their net present values. Excludes accretion associated with asset retirement obligations.

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Amount of amortization expense attributable to debt issuance costs.

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Amount of a favorable spread to a debt holder between the amount of debt being converted and the value of the securities received upon conversion. This is an embedded conversion feature of convertible debt issued that is in-the-money at the commitment date.

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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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