Financial Instruments - Fair Value Assets and Liabilities Measured on Recurring Basis (Details) - Recurring - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Restricted investment:
Rabbi Trusts	$ 45,910	$ 36,982
Marketable equity and fixed income securities	49,360	25,939
Quoted Prices in Active Markets (Level 1)
Restricted investment:
Rabbi Trusts	7,014
Marketable equity and fixed income securities	22,691
Significant Other Observable Inputs (Level 2)
Restricted investment:
Rabbi Trusts	38,896	36,982
Marketable equity and fixed income securities	26,669	25,939
Interest Rate Swap
Restricted investment:
Interest rate swap derivatives	6,094	4,613
Interest Rate Swap | Significant Other Observable Inputs (Level 2)
Restricted investment:
Interest rate swap derivatives	$ 6,094	$ 4,613