Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Carryforwards
Increase (decrease) in valuation allowance	$ 16,300	$ 16,800
Net operating loss carryforwards	656,900
Operating loss carryforwards subject to expiry	196,400
Deferred income tax assets (liabilities)
Net operating loss carryforwards	139,610	133,031
Capitalized start-up costs	5,721	6,538
Research and development credit carryforwards	15,326	13,121
Research and development expenditures	16,284	8,853
Stock-based compensation	1,684	1,695
Fair value of derivative liability	22	5,136
Other	3,181	2,143
Gross total deferred tax asset	181,828	170,517
Valuation allowance	(179,517)	(163,255)
Total net deferred tax assets	2,311	7,262
Right of use amortization	(1,774)	(896)
Amortization of debt discount	(537)	(6,366)
Total deferred tax liability	(2,311)	(7,262)
Net deferred tax assets	0	$ 0
Research and Development Credit Carryforwards
Carryforwards
Tax credit carryforwards	$ 15,300