Financial Instruments - Fair Value Assets and Liabilities Measured on Recurring Basis (Details) - Recurring - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Restricted investment:
Rabbi Trusts	$ 54,299	$ 51,247
Marketable equity and fixed income securities	52,524	47,382
Other non-current assets	19,365	18,887
Quoted Prices in Active Markets (Level 1)
Restricted investment:
Rabbi Trusts	9,814	9,547
Marketable equity and fixed income securities	25,836	19,010
Significant Other Observable Inputs (Level 2)
Restricted investment:
Rabbi Trusts	44,485	41,700
Marketable equity and fixed income securities	26,688	28,372
Other non-current assets	19,365	18,887
Interest Rate Swap
Restricted investment:
Interest rate swap derivatives	4,881	3,849
Interest Rate Swap | Significant Other Observable Inputs (Level 2)
Restricted investment:
Interest rate swap derivatives	$ 4,881	$ 3,849