Fair Value Measurements - Debt at Carrying and Fair Value (Details) - USD ($)	Dec. 31, 2021	Dec. 31, 2020
Subsidiaries [Member] | Carrying Amount | Income Approach Valuation Technique
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt, Excluding Current Maturities, Fair Value Disclosure	$ 4,784,719,000	$ 4,338,044,000
Subsidiaries [Member] | Carrying Amount | Income Approach Valuation Technique | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unamortized Debt Issuance Expense	22,800,000	22,900,000
Long-term Debt, Fixed Rate, Net of Discount, Fair Value Disclosure	4,784,719,000	4,338,044,000
Subsidiaries [Member] | Total | Income Approach Valuation Technique
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt, Excluding Current Maturities, Fair Value Disclosure	6,145,639,000	6,086,358,000
Subsidiaries [Member] | Total | Income Approach Valuation Technique | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt, Fixed Rate, Net of Discount, Fair Value Disclosure	6,145,639,000	6,086,358,000
Parent Company [Member] | Carrying Amount | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Notes Receivable, Fair Value Disclosure	53,200,000	52,700,000
Parent Company [Member] | Carrying Amount | Income Approach Valuation Technique
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt, Excluding Current Maturities, Fair Value Disclosure	6,203,766,000	5,892,440,000
Parent Company [Member] | Carrying Amount | Income Approach Valuation Technique | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unamortized Debt Issuance Expense	22,700,000	22,700,000
Long-term Debt, Fixed Rate, Net of Discount, Fair Value Disclosure	6,170,466,000	5,667,740,000
Long-term Debt, Variable Rate, Net of Discount, Fair Value Disclosure	33,300,000	224,700,000
Parent Company [Member] | Total | Income Approach Valuation Technique
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt, Excluding Current Maturities, Fair Value Disclosure	7,803,196,000	7,980,646,000
Parent Company [Member] | Total | Income Approach Valuation Technique | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt, Fixed Rate, Net of Discount, Fair Value Disclosure	7,769,896,000	7,755,946,000
Long-term Debt, Variable Rate, Net of Discount, Fair Value Disclosure	$ 33,300,000	$ 224,700,000