Credit Facility - February 2015 Amended Credit Facility (Details)	Apr. 30, 2021	Feb. 18, 2018 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Letter of Credit
Line of Credit Facility [Line Items]
Revolving credit facility		$ 10,000,000
Third Amended Credit Facility
Line of Credit Facility [Line Items]
Revolving credit facility		35,000,000
Increase in revolving credit facility (up to)		15,000,000
Aggregate maximum of revolving credit facility		$ 50,000,000
Adjusted quick ratio (at least)		1.25
Outstanding Balance on Credit Facility			$ 0
Amount available under the credit facility			32,600,000	$ 32,200,000
Letters of credit outstanding under the subfacility			$ 2,400,000	$ 2,800,000
Third Amended Credit Facility | Minimum
Line of Credit Facility [Line Items]
Unused revolving line facility fee (as a percent)	0.00%
Third Amended Credit Facility | Maximum
Line of Credit Facility [Line Items]
Unused revolving line facility fee (as a percent)	0.15%
Third Amended Credit Facility | Prime Rate | Minimum
Line of Credit Facility [Line Items]
Interest rate	(0.25%)
Third Amended Credit Facility | Prime Rate | Maximum
Line of Credit Facility [Line Items]
Interest rate	0.25%
Third Amended Credit Facility | London Interbank Offered Rate (LIBOR) | Minimum
Line of Credit Facility [Line Items]
Interest rate	1.75%
Third Amended Credit Facility | London Interbank Offered Rate (LIBOR) | Maximum
Line of Credit Facility [Line Items]
Interest rate	2.25%