Long-Term Debt - Schedule of Debt (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Apr. 30, 1998
Debt Instrument [Line Items]
Gross	$ 1,887,617	$ 1,687,879
Debt Issuance Costs	(16,384)	(21,319)
Net	(1,871,233)	(1,666,560)
Less current portion of long-term debt	43,230	56,022
Debt Issuance Costs, Current	0	0
Long-term debt, net of current portion, gross	1,844,387	1,631,857
Long-term debt, net of current portion, debt issuance costs	(16,384)	(21,319)
Long-term debt, net of current portion	1,828,003	1,610,538
Revolving line of credit \| Line of Credit Due May 2024
Debt Instrument [Line Items]
Gross	300,000	0
Debt Issuance Costs	(4,930)	(6,425)
Net	$ (295,070)	(6,425)
Debt instrument, weighted average interest rate percentage	1.64%
Term Loan Facility \| Term Loan Due May 2024
Debt Instrument [Line Items]
Gross	$ 1,572,000	1,672,188
Debt Issuance Costs	(11,431)	(14,868)
Net	$ (1,560,569)	(1,657,320)
Debt instrument, weighted average interest rate percentage	1.77%
Senior Notes \| 7.55% senior debentures due April 2028
Debt Instrument [Line Items]
Gross	$ 9,531	9,524
Debt Issuance Costs	(23)	(26)
Net	$ (9,508)	(9,498)
Debt instrument, stated rate percentage	7.55%		7.55%
Other debt \| Various interest rates with maturities through March 2024
Debt Instrument [Line Items]
Gross	$ 6,086	6,167
Debt Issuance Costs	0	0
Net	$ (6,086)	$ (6,167)

Long-term Debt, Excluding Current Maturities Gross

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Unamortized Debt Issuance Expense, Net

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- Definition

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

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Contractual interest rate for funds borrowed, under the debt agreement.

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Amount, after accumulated amortization, of debt issuance costs classified as current. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt, classified as current. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Amount after unamortized (discount) premium and debt issuance costs of long-term debt classified as noncurrent and excluding amounts to be repaid within one year or the normal operating cycle, if longer. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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The remaining balance of debt issuance expenses that were capitalized and are being amortized against income over the lives of the respective bond issues. This does not include the amounts capitalized as part of the cost of the utility plant or asset.

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