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Face (par) amount of debt instrument at time of issuance.

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

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Amount, after accumulated amortization, of debt discount.

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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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Amount of long-term debt and lease obligation, classified as noncurrent.

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Amount before tax of reclassification adjustment from accumulated other comprehensive income of accumulated gain (loss) realized from derivative instruments designated and qualifying as the effective portion of cash flow hedges and an entity's share of an equity investee's deferred hedging gain (loss).

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Amount of long-term debt classified as other, payable after one year or the operating cycle, if longer.

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The cash inflow during the period from additional borrowings in aggregate debt. Includes proceeds from short-term and long-term debt.

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The cash outflow for debt initially having maturity due after one year or beyond the normal operating cycle, if longer.

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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 (Details) - USD ($)		9 Months Ended	12 Months Ended
Debt (Details) - USD ($)	Oct. 01, 2019	Sep. 30, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Oct. 03, 2019
Debt Instrument [Line Items]
Loss on early extinguishment of debt			$ (3,000,000)	$ 0	$ (51,000,000)
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, before Tax			0	0	47,000,000
Repayments of Long-term Debt			600,000,000	0	2,764,000,000
Other Long-term Debt, Noncurrent			5,536,000,000	5,536,000,000
Unamortized Discount			(7,000,000)	(8,000,000)
Unamortized Debt Issuance Expense			(28,000,000)	(29,000,000)
Total long-term debt due after one year			5,501,000,000	5,499,000,000
Debt Immediately Due If Change In Control			236,000,000
Proceeds from Issuance of Debt	$ 600,000,000
Long-term Debt, Fiscal Year Maturity [Abstract]
Year 1			0
Year 2			0
Year 3			1,035,000,000
Year 4			401,000,000
Year 5			200,000,000
Thereafter			3,900,000,000
Other Long-term Debt, Noncurrent			$ 5,536,000,000	5,536,000,000
Senior Unsecured Notes Due 2020 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage			2.70%
Other Long-term Debt, Noncurrent			$ 0	600,000,000		$ 600,000,000
Long-term Debt, Fiscal Year Maturity [Abstract]
Other Long-term Debt, Noncurrent			$ 0	600,000,000		$ 600,000,000
Senior Unsecured Notes Due 2022 [A] [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage			2.80%
Other Long-term Debt, Noncurrent				1,000,000,000
Long-term Debt, Fiscal Year Maturity [Abstract]
Other Long-term Debt, Noncurrent				1,000,000,000
Senior Unsecured Notes Due 2022 [B] [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage			9.375%
Other Long-term Debt, Noncurrent			$ 32,000,000	32,000,000
Long-term Debt, Fiscal Year Maturity [Abstract]
Other Long-term Debt, Noncurrent			32,000,000	32,000,000
Series Medium Term Notes Due 2022 [Member]
Debt Instrument [Line Items]
Other Long-term Debt, Noncurrent			3,000,000	3,000,000
Long-term Debt, Fiscal Year Maturity [Abstract]
Other Long-term Debt, Noncurrent			$ 3,000,000	3,000,000
Senior Unsecured Notes Due 2023 [A] [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage			8.50%
Other Long-term Debt, Noncurrent			$ 70,000,000	70,000,000
Long-term Debt, Fiscal Year Maturity [Abstract]
Other Long-term Debt, Noncurrent			$ 70,000,000	70,000,000
Senior Unsecured Notes Due 2023 [B] [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage			8.125%
Other Long-term Debt, Noncurrent			$ 131,000,000	131,000,000
Long-term Debt, Fiscal Year Maturity [Abstract]
Other Long-term Debt, Noncurrent			$ 131,000,000	131,000,000
Senior Unsecured Notes Due 2025 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage			3.85%
Other Long-term Debt, Noncurrent			$ 900,000,000	900,000,000
Long-term Debt, Fiscal Year Maturity [Abstract]
Other Long-term Debt, Noncurrent			$ 900,000,000	900,000,000
Senior Unsecured Notes Due 2032 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage			6.80%
Other Long-term Debt, Noncurrent			$ 550,000,000	550,000,000
Long-term Debt, Fiscal Year Maturity [Abstract]
Other Long-term Debt, Noncurrent			$ 550,000,000	550,000,000
Notes Due 2027 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage			4.40%
Other Long-term Debt, Noncurrent			$ 1,000,000,000	1,000,000,000
Long-term Debt, Fiscal Year Maturity [Abstract]
Other Long-term Debt, Noncurrent			$ 1,000,000,000	1,000,000,000
Senior Unsecured Notes Due 2037 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage			6.60%
Other Long-term Debt, Noncurrent			$ 750,000,000	750,000,000
Long-term Debt, Fiscal Year Maturity [Abstract]
Other Long-term Debt, Noncurrent			$ 750,000,000	750,000,000
Senior Unsecured Notes Due 2045 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage			5.20%
Other Long-term Debt, Noncurrent			$ 500,000,000	500,000,000
Long-term Debt, Fiscal Year Maturity [Abstract]
Other Long-term Debt, Noncurrent			500,000,000	500,000,000
Interest Rate Swap [Member]
Debt Instrument [Line Items]
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, before Tax					$ 46,000,000
Interest Rate Swap [Member] \| Not Designated as Hedging Instrument [Member]
Debt Instrument [Line Items]
Cash Proceeds Received from Derivatives		$ 54,000,000
Senior Unsecured Note Due 2022 [Member]
Debt Instrument [Line Items]
Total long-term debt due after one year			1,000,000,000
Sub-series A-1 Bonds [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount			$ 200,000,000
Debt Instrument, Interest Rate, Stated Percentage			2.00%
Sub-series A-2 Bonds [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount			$ 200,000,000
Debt Instrument, Interest Rate, Stated Percentage			2.10%
St. John the Baptist Parish, State of Louisiana Revenue Bonds Due 2037 [Member]
Debt Instrument [Line Items]
Revenue Refunding Bond			$ 400,000,000	$ 1,000,000,000.0
Sub-series A-3 Bonds [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount			$ 200,000,000
Debt Instrument, Interest Rate, Stated Percentage			2.20%
Senior Unsecured Notes Due 2020 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage						2.70%