Financial Instruments - Fair Value Assets and Liabilities Measured on Recurring Basis (Details) - Recurring - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Restricted investments:
Rabbi Trust	$ 42,937	$ 35,749
Marketable equity and fixed income securities	11,551
Fixed income securities	1,927	1,932
Significant Other Observable Inputs (Level 2)
Restricted investments:
Rabbi Trust	42,937	35,749
Marketable equity and fixed income securities	11,551
Fixed income securities	1,927	1,932
Interest Rate Swap
Liabilities:
Interest rate swap derivatives	3,195	6,015
Interest Rate Swap | Significant Other Observable Inputs (Level 2)
Liabilities:
Interest rate swap derivatives	$ 3,195	$ 6,015