Income Taxes - Narrative (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Operating Loss Carryforwards [Line Items]
Valuation allowance	$ 131,839	$ 104,585
Initial deferred tax liability related to 2018 convertible debt	2,933	7,229
Unrecognized tax benefits	7,556	4,866	$ 3,712	$ 2,983
Uncertain tax positions that would impact the effective tax rate	100
PPP Loan - 1% interest
Operating Loss Carryforwards [Line Items]
Initial deferred tax liability related to 2018 convertible debt				$ 14,000
Federal
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	372,100
Operating loss carryforwards, subject to expiration	170,600
Operating loss carryforwards, not subject to expiration	201,400
Federal | R&D tax credits
Operating Loss Carryforwards [Line Items]
Tax credits		13,500
State
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	$ 361,800
State | R&D tax credits
Operating Loss Carryforwards [Line Items]
Tax credits		$ 10,900