Stockholders' Equity - Summary of activity under Employee Stock Purchase Plan (Details) - Employee stock purchase plan - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Summary of the Employee Stock Purchase Plan activity
Outstanding and exercisable, beginning of period (in shares)	361,719	363,218	332,659	328,533
Granted (in shares)	0	0	212,716	235,572
Exercised (in shares)	(3,504)	(9,927)	(17,871)	(28,943)
Forfeited (in shares)	(6,659)	(11,762)	(36,154)	(51,559)
Expired (in shares)	0	0	(139,794)	(142,074)
Outstanding and exercisable, end of period (in shares)	351,556	341,529	351,556	341,529