Fair Value Measurements (Estimated Fair Values of Financial Instruments) (Details) - USD ($) $ in Thousands		Jun. 30, 2023	Dec. 31, 2022
Carrying Amount [Member] | Level 2 [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Long-term debt, including current portion	[1]	$ (1,035,329)	$ (1,035,004)
Carrying Amount [Member] | Level 2 [Member] | Interest rate contracts [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Derivative assets related to interest rate swaps		139,787	144,583
Carrying Amount [Member] | Level 2 [Member] | Term Loans [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Long-term debt, including current portion		(969,594)	(969,269)
Carrying Amount [Member] | Level 2 [Member] | Revenue bonds [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Long-term debt, including current portion		(65,735)	(65,735)
Carrying Amount [Member] | Level 3 [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Company owned life insurance asset (COLI)		4,699	4,311
Fair Value [Member] | Level 2 [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Long-term debt, including current portion	[1]	(1,027,006)	(1,026,234)
Fair Value [Member] | Level 2 [Member] | Interest rate contracts [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Derivative assets related to interest rate swaps		139,787	144,583
Fair Value [Member] | Level 2 [Member] | Term Loans [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Long-term debt, including current portion		(962,002)	(961,632)
Fair Value [Member] | Level 2 [Member] | Revenue bonds [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Long-term debt, including current portion		(65,004)	(64,602)
Fair Value [Member] | Level 3 [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Company owned life insurance asset (COLI)		$ 4,699	$ 4,311

[1] The carrying amount of long-term debt includes principal and unamortized discounts.