Stockholders' Equity - Summary of activity under Employee Stock Purchase Plan (Details) - Employee stock purchase plan - shares	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Summary of the Employee Stock Purchase Plan activity
Outstanding and exercisable, beginning of period (in shares)	415,299	370,696	341,647	332,659
Granted (in shares)	0	0	253,200	212,716
Exercised (in shares)	(3,012)	(2,463)	(18,977)	(14,367)
Forfeited (in shares)	(22,873)	(6,514)	(42,034)	(29,495)
Expired (in shares)	0	0	(144,422)	(139,794)
Outstanding and exercisable, end of period (in shares)	389,414	361,719	389,414	361,719