Summary of Significant Accounting Policies - Defined Contribution Plan (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accounting Policies [Abstract]
Employer matching contribution, percent of match	40.00%
Employer matching contribution, percent of employees' gross pay	6.00%
Vesting period	5 years
Employer contributions	$ 2.0	$ 1.1	$ 0.7