Financial Instruments and Fair Value Measurements - Carrying Amount and Fair Value (Details) - Nonrecurring - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Carrying Value
Financial instruments and fair value measurements
Debt	$ 262,091	$ 227,474
Fair Value
Financial instruments and fair value measurements
Debt	261,882	224,664
Level 1 | Carrying Value | U.S. Treasury Bills
Financial instruments and fair value measurements
Investments held by SPEs	4,754	5,132
Level 1 | Fair Value | U.S. Treasury Bills
Financial instruments and fair value measurements
Investments held by SPEs	4,873	5,475
Level 2 | Carrying Value | Fixed-rate debt
Financial instruments and fair value measurements
Debt	98,192	129,532
Level 2 | Carrying Value | Variable rate debt
Financial instruments and fair value measurements
Debt	163,899	97,942
Level 2 | Fair Value | Fixed-rate debt
Financial instruments and fair value measurements
Debt	97,983	126,722
Level 2 | Fair Value | Variable rate debt
Financial instruments and fair value measurements
Debt	163,899	97,942
Level 3 | Carrying Value
Financial instruments and fair value measurements
Debt	177,637	177,566
Level 3 | Carrying Value | Time deposit
Financial instruments and fair value measurements
Investments held by SPEs	200,000	200,000
Level 3 | Fair Value
Financial instruments and fair value measurements
Debt	193,575	204,802
Level 3 | Fair Value | Time deposit
Financial instruments and fair value measurements
Investments held by SPEs	$ 200,000	$ 200,000