Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Operating Loss Carryforwards [Line Items]
Federal statutory income tax rate	21.00%	21.00%
Federal Operating loss carryforwards	$ 222,900
State Operating loss carryforwards	227,000
Federal Operating loss carryforwards subject to expiration	37,200
Federal Operating loss carryforwards subject to expiration indefinitely	185,700
Research and development tax credit carryforwards	13,525	$ 3,824
Increase in gross deferred tax assets, before valuation allowance	52,200
Accrued interest or penalties	0	0
Uncertain tax positions	0	$ 0
U.S. federal
Operating Loss Carryforwards [Line Items]
Research and development tax credit carryforwards	9,500
State
Operating Loss Carryforwards [Line Items]
Research and development tax credit carryforwards	$ 5,100