Employee Benefit Plan (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2014
Employee Benefit Plan
Employee defined contribution plan expense	$ 0.1
Assets contributed to 401(k) Plan				$ 7.9
Restricted investments		$ 1.2
Compensation expense for assets allocated to participants	$ 1.2	1.2	$ 1.1
First 3% of employee contributions
Employee Benefit Plan
Percentage employer matches of the employee's percentage contribution	100.00%
Percentage of employee's gross pay for which the employer contributes a matching contribution (as a percent)	3.00%
3% - 5% of employee contributions
Employee Benefit Plan
Percentage employer matches of the employee's percentage contribution	50.00%
Percentage of employee's gross pay for which the employer contributes a matching contribution (as a percent)	2.00%
Low end of gross pay (as a percent)	3.00%
High end of gross pay (as a percent)	5.00%
Restricted | Maximum
Employee Benefit Plan
Gain (loss) on assets	$ 0.1	$ 0.1	$ (0.1)