Borrowing Arrangements - Bank Line of Credit (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021	Oct. 31, 2021
Bank line of credit
Borrowings outstanding under the bank revolving line of credit	$ 40,000	$ 0
Revolving line of credit
Bank line of credit
Maximum borrowing capacity under the bank revolving line of credit			$ 100,000
Maximum letter of credit sublimit under the bank revolving line of credit			$ 25,000
Borrowings outstanding under the bank revolving line of credit	40,000
Outstanding amount of letters of credit under the bank revolving line of credit	900
Available borrowing capacity under the bank revolving line of credit, due to outstanding letters of credit	59,100
Available amount of letters of credit under the bank revolving line of credit	$ 24,100
Fixed interest rate of credit facility (as a percent)	1.92%
Fair value of investments pledged as collateral on the bank revolving line of credit	$ 108,700