Financial Instruments - Fair Value Assets and Liabilities Measured on Recurring Basis (Details) - Recurring - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Restricted investment:
Rabbi Trusts	$ 46,372	$ 36,982
Marketable equity and fixed income securities	44,297	25,939
Quoted Prices in Active Markets (Level 1)
Restricted investment:
Rabbi Trusts	7,014
Marketable equity and fixed income securities	17,231
Significant Other Observable Inputs (Level 2)
Restricted investment:
Rabbi Trusts	39,358	36,982
Marketable equity and fixed income securities	27,066	25,939
Interest Rate Swap
Restricted investment:
Interest rate swap derivatives	4,360	4,613
Interest Rate Swap | Significant Other Observable Inputs (Level 2)
Restricted investment:
Interest rate swap derivatives	$ 4,360	$ 4,613