401(k) Plan (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
401(k) Plan
Minimum age of employee eligible to participate in the plan	21 years
Employer contributions (as a percent)	100.00%
Percentage of eligible compensation, matched by the employer	4.00%
Employee's elective deferral, maximum contribution	$ 0.3
Matching contribution made	$ 4.9	$ 3.2	$ 2.7