Carrying value as of the balance sheet date of obligations incurred and payable, pertaining to costs that are statutory in nature, are incurred on contractual obligations, or accumulate over time and for which invoices have not yet been received or will not be rendered. Examples include taxes, interest, rent and utilities. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

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Background and Basis of Presentation (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Accrued liabilities	$ 72,644		$ 68,565
Equity	1,337,882	$ 1,243,343	609,635	$ 498,378	$ 462,927	$ 498,829
Additional Paid-In Capital
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Equity	1,706,855	1,645,352	1,030,577	907,908	890,258	916,095
Accumulated Deficit
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Equity	$ (368,148)	$ (400,912)	(422,601)	$ (411,504)	$ (422,093)	(416,292)
Cumulative Effect, Period of Adoption, Adjustment
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Equity			(378,138)			(88)
Cumulative Effect, Period of Adoption, Adjustment \| Additional Paid-In Capital
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Equity			(465,006)
Cumulative Effect, Period of Adoption, Adjustment \| Accumulated Deficit
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Equity			86,868			$ (88)
Cumulative Effect, Period of Adoption, Adjustment \| Accounting Standards Update 2020-06 \| Senior Notes
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Equity			378,100
Cumulative Effect, Period of Adoption, Adjustment \| Accounting Standards Update 2020-06 \| Additional Paid-In Capital
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Equity			(465,000)
Cumulative Effect, Period of Adoption, Adjustment \| Accounting Standards Update 2020-06 \| Accumulated Deficit
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Equity			86,900
Revision of Prior Period, Reclassification, Adjustment
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Current operating lease liabilities			6,600
Accrued liabilities			$ 6,600