Credit Agreement - Schedule of Credit Agreement (Detail) - Credit Agreement [Member] - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2021	Dec. 31, 2020
Credit Agreement:
Credit facility remaining availability		$ 124,082	$ 48,582
Outstanding letters of credit		918	1,418
Availability of additional letters of credit	[1]	$ 124,082	$ 23,582
Line of credit facility, interest rate		0.00%	0.00%
Commitment fee rate		0.30%	0.30%
Letter of credit fee rate	[2]	3.00%	1.25%

[1] The letters of credit availability under the credit agreement with Wintrust is up to the borrowing limit of $125.0 million. For the previous credit agreement with BMO Harris Bank N.A., a sublimit of $25.0 million under the credit agreement was part of, not in addition to, the $50.0 million borrowing limit under the credit agreement.

[2] The 2021 letter of credit fee rate is based on prime minus 1.0%, subject to a minimum rate of 3.0%. The prime rate as of December 31, 2021 was 3.25%, which would yield a 2.25% fee rate, therefore the minimum rate of 3.0% is reflected in the table above.