Financial Instruments - Fair Value Assets and Liabilities Measured on Recurring Basis (Details) - Recurring - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Restricted investment:
Rabbi Trusts	$ 53,403	$ 51,247
Marketable equity and fixed income securities	52,250	47,382
Other non-current assets	19,186	18,887
Quoted Prices in Active Markets (Level 1)
Restricted investment:
Rabbi Trusts	9,692	9,547
Marketable equity and fixed income securities	23,366	19,010
Significant Other Observable Inputs (Level 2)
Restricted investment:
Rabbi Trusts	43,711	41,700
Marketable equity and fixed income securities	28,884	28,372
Other non-current assets	19,186	18,887
Interest Rate Swap
Restricted investment:
Interest rate swap derivatives	4,733	3,849
Interest Rate Swap | Significant Other Observable Inputs (Level 2)
Restricted investment:
Interest rate swap derivatives	$ 4,733	$ 3,849