Stock-Based Compensation - Employee Stock Purchase Plan (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	$ 29,176,000	$ 20,603,000	$ 13,429,000
Employee stock purchase plan | Employee Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares reserved for future grant (in shares)	1,974,251
Shares reserved for grant, annual increase period (in years)	9 years
Annual automatic increase in shares available, percentage of each class of common stock outstanding (percent)	1.00%
Annual automatic increase in shares available (in shares)	1,500,000
Fair market value purchase discount (percent)	90.00%
Maximum number of shares participant may purchase, fair market value (not to exceed)	$ 15,000
Maximum number of shares participant may purchase as a percentage of base compensation (not to exceed) (percent)	10.00%
Discount of the market value on the date of purchase (not to exceed) (percent)	10.00%
Shares purchased by employees (in shares)	29,933	26,811	29,131
Total stock-based compensation expense	$ 200,000	$ 200,000	$ 100,000
Purchase period	6 months