Restatement of Previously Issued Audited Financial Statements - Balance Sheet (Details) - USD ($) $ in Thousands		Dec. 31, 2020		Dec. 31, 2019		Dec. 31, 2018
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Assets		$ 232,626		$ 134,637
Current Liabilities		21,681		569,496
Other liabilities, non-current - Note 8		1,650		0
Debt, net, non-current - Note 9		142,665		0
Royalty obligation, non-current - Note 10		29,839		0
Asset retirement obligation, non-current - Note 12		4,785		4,374
Warrant liabilities, non-current - Note 11		15,389		18
Total liabilities		216,009		573,888
Common stock, $0.0001 par value; 400,000,000 shares authorized; 59,901,306 issued and outstanding at December 31, 2020; and 345,431 issued and 323,328 outstanding at December 31, 2019	[1]	6		0
Additional paid-in capital	[1]	537,370		5,187
Accumulated deficit	[1]	(520,759)		(444,438)
Total stockholders' equity (deficit)		16,617	[1]	(439,251)	[1]	$ (340,356)
Total liabilities and stockholders' equity (deficit)		232,626		$ 134,637
As Previously Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Assets		232,626
Current Liabilities		21,681
Other liabilities, non-current - Note 8		1,712
Debt, net, non-current - Note 9		142,665
Royalty obligation, non-current - Note 10		29,839
Asset retirement obligation, non-current - Note 12		4,785
Warrant liabilities, non-current - Note 11		0
Total liabilities		200,682
Common stock, $0.0001 par value; 400,000,000 shares authorized; 59,901,306 issued and outstanding at December 31, 2020; and 345,431 issued and 323,328 outstanding at December 31, 2019		6
Additional paid-in capital		548,975
Accumulated deficit		(517,037)
Total stockholders' equity (deficit)		31,944
Total liabilities and stockholders' equity (deficit)		232,626
Restatement Adjustment
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Assets		0
Current Liabilities		0
Other liabilities, non-current - Note 8		(62)
Debt, net, non-current - Note 9		0
Royalty obligation, non-current - Note 10		0
Asset retirement obligation, non-current - Note 12		0
Warrant liabilities, non-current - Note 11		15,389
Total liabilities		15,327
Common stock, $0.0001 par value; 400,000,000 shares authorized; 59,901,306 issued and outstanding at December 31, 2020; and 345,431 issued and 323,328 outstanding at December 31, 2019		0
Additional paid-in capital		(11,605)
Accumulated deficit		(3,722)
Total stockholders' equity (deficit)		(15,327)
Total liabilities and stockholders' equity (deficit)		$ 0

[1] Retroactively restated for the reverse recapitalization as described in Note 2 - Summary of Significant Accounting Policies.