Financial Instruments and Fair Value Measurements - Carrying Amount and Fair Value (Details) - Nonrecurring - USD ($) $ in Thousands	Mar. 31, 2025	Dec. 31, 2024
Carrying Value
Financial instruments and fair value measurements
Debt	$ 440,169	$ 442,716
Fair Value
Financial instruments and fair value measurements
Debt	392,593	391,356
Level 1 | Carrying Value | U.S. Treasury Bills
Financial instruments and fair value measurements
Investments held by SPEs	2,751	3,143
Level 1 | Fair Value | U.S. Treasury Bills
Financial instruments and fair value measurements
Investments held by SPEs	2,715	3,078
Level 2 | Carrying Value | Fixed-rate debt
Financial instruments and fair value measurements
Debt	284,510	258,135
Level 2 | Carrying Value | Variable rate debt
Financial instruments and fair value measurements
Debt	155,659	184,581
Level 2 | Fair Value | Fixed-rate debt
Financial instruments and fair value measurements
Debt	236,934	206,775
Level 2 | Fair Value | Variable rate debt
Financial instruments and fair value measurements
Debt	155,659	184,581
Level 3 | Carrying Value
Financial instruments and fair value measurements
Senior Notes held by SPE	178,567	178,484
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
Senior Notes held by SPE	180,373	178,473
Level 3 | Fair Value | Time deposit
Financial instruments and fair value measurements
Investments held by SPEs	$ 200,000	$ 200,000