Employee Benefit Plans - Fair Value Hierarchy (Details) - Post-Retirement Medical Benefits - USD ($) $ in Thousands	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Employee benefit plans
Total investments measured at fair value	$ 14,456	$ 12,827	$ 11,240
Fair Value
Employee benefit plans
Total investments measured at fair value	14,456	12,827
Level 1
Employee benefit plans
Total investments measured at fair value	14,456	12,827
Level 2
Employee benefit plans
Total investments measured at fair value	0	0
Level 3
Employee benefit plans
Total investments measured at fair value	0	0
Cash equivalents | Fair Value
Employee benefit plans
Total investments measured at fair value	110	189
Cash equivalents | Level 1
Employee benefit plans
Total investments measured at fair value	110	189
Cash equivalents | Level 2
Employee benefit plans
Total investments measured at fair value	0	0
Cash equivalents | Level 3
Employee benefit plans
Total investments measured at fair value	0	0
Fixed income fund | Fair Value
Employee benefit plans
Total investments measured at fair value	5,818	5,001
Fixed income fund | Level 1
Employee benefit plans
Total investments measured at fair value	5,818	5,001
Fixed income fund | Level 2
Employee benefit plans
Total investments measured at fair value	0	0
Fixed income fund | Level 3
Employee benefit plans
Total investments measured at fair value	0	0
U.S. equity securities | Fair Value
Employee benefit plans
Total investments measured at fair value	8,528	7,637
U.S. equity securities | Level 1
Employee benefit plans
Total investments measured at fair value	8,528	$ 7,637
U.S. equity securities | Level 2
Employee benefit plans
Total investments measured at fair value	0
U.S. equity securities | Level 3
Employee benefit plans
Total investments measured at fair value	$ 0