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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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Gross amount of debt extinguished.

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Difference between the fair value of payments made and the carrying amount of debt which is extinguished prior to maturity.

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Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

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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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Debt (2016 Credit Facility - Narrative) (Details) - USD ($)		12 Months Ended
	Apr. 26, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Jun. 30, 2016	Dec. 31, 2013
Debt Instrument [Line Items]
Debt Instrument		$ 2,262,000,000	$ 2,342,000,000
Extinguishment of debt	$ 1,191,000,000
Gain (Loss) on Early Extinguishment of Debt		8,000,000	(17,000,000)	$ (70,000,000)
Unamortized debt expense		$ 19,000,000	$ 23,000,000
2013 Revolving Credit Facility \| Revolving Credit Facility
Debt Instrument [Line Items]
Maximum borrowing capacity					$ 66,000,000
2016 Credit Agreement
Debt Instrument [Line Items]
Maximum borrowing capacity					1,934,000,000
Line of Credit \| 2013 Revolving Credit Facility \| Revolving Credit Facility
Debt Instrument [Line Items]
Maximum borrowing capacity						$ 2,000,000,000.0
Line of Credit \| 2016 Revolving Credit Facility Maturing December 2020 \| Revolving Credit Facility
Debt Instrument [Line Items]
Maximum borrowing capacity					743,000,000
Unamortized debt expense	4,000,000
Term Loan \| 2016 Term Loan Due December 2020
Debt Instrument [Line Items]
Debt Instrument					$ 1,191,000,000
Gain (Loss) on Early Extinguishment of Debt	$ (8,000,000)