Long-Term Debt (Narrative) (Details)	1 Months Ended	12 Months Ended
	May 31, 2020 USD ($)	Dec. 31, 2021 USD ($) type_of_borrowing business_day lender	Nov. 30, 2021 USD ($)	Dec. 31, 2020 USD ($)	May 06, 2020 USD ($)	May 05, 2020	Mar. 31, 2020	Dec. 31, 2019
Short-term Debt [Line Items]
Maximum borrowing capacity		$ 1,200,000,000		$ 1,200,000,000
Number of lenders in syndicate | lender		12
Credit facility outstanding		$ 0		$ 0
Number of types of borrowing that may be elected under the facility | type_of_borrowing		5
Number of business days' notice to terminate facility | business_day		3
Letters of credit
Short-term Debt [Line Items]
Maximum borrowing capacity		$ 125,000,000.0
Revolving credit facility
Short-term Debt [Line Items]
Maximum borrowing capacity		1,200,000,000
Letters of credit
Short-term Debt [Line Items]
Credit facility outstanding		$ 0
Line of Credit
Short-term Debt [Line Items]
Maturities (term)	5 years
Maximum borrowing capacity	$ 1,200,000,000
Leverage ratio to EBITDA		3.50					3.50	4.25
Secured debt limit, percentage of total consolidated assets		15.00%			5.00%	15.00%
Excess of without planned expenditures		$ 750,000,000.0			$ 300,000,000.0
Line of Credit | Revolving credit facility
Short-term Debt [Line Items]
Maximum borrowing capacity		$ 1,200,000,000
Line of Credit | Debt Covenant 1
Short-term Debt [Line Items]
Leverage ratio to EBITDA					4.75
Line of Credit | Debt Covenant 2
Short-term Debt [Line Items]
Leverage ratio to EBITDA		4.00			4.25
Line of Credit | Debt Covenant 3
Short-term Debt [Line Items]
Leverage ratio to EBITDA					3.75
Line of Credit | Debt Covenant 4
Short-term Debt [Line Items]
Leverage ratio to EBITDA					3.25
Term notes | Senior Notes, Due 2022
Short-term Debt [Line Items]
Stated percentage		3.40%
Term notes | Senior Notes, Due 2051
Short-term Debt [Line Items]
Debt instrument amount issued			$ 500,000,000.0
Stated percentage			3.50%