Risk Management and Fair Values (Narrative) (Details) TWh in Millions, $ in Millions	3 Months Ended			9 Months Ended		12 Months Ended
	Dec. 31, 2019 TWh	Sep. 30, 2019 USD ($) GWh MMBTU	Sep. 30, 2018 USD ($)	Sep. 30, 2019 USD ($) GWh MMBTU	Sep. 30, 2018 USD ($)	Dec. 31, 2018 USD ($) counterparty
Risk Management and Fair Values [Abstract]
Cash flow hedges relating to power sales as part of net unrealized gains				$ 42.0
Reclassified from accumulated other comprehensive income (OCI) to operating revenues				30.0
Maturity of cash flow hedges, Tax		$ 4.0	$ (2.0)	$ 16.0	$ (8.0)
Maximum length of time over which Company is currently hedging the variability in future cash flows for forecasted power transactions, years				1 year 6 months
Total volume of natural gas swaps outstanding (MMBtu) | MMBTU		40,346,000		40,346,000
Total volume of fixed transmission rights outstanding | GWh		79,459		79,459
Change in cash flow hedges due to ineffectiveness			(3.1)		(5.2)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset and Liability Unrealized Gains (Loss) Included in Earnings		$ (1.2)	$ 1.7	$ (4.7)	$ 1.1
Entergy Arkansas [Member]
Risk Management and Fair Values [Abstract]
Total volume of fixed transmission rights outstanding | GWh		17,898		17,898
Entergy Louisiana [Member]
Risk Management and Fair Values [Abstract]
Total volume of natural gas swaps outstanding (MMBtu) | MMBTU		32,880,000		32,880,000
Total volume of fixed transmission rights outstanding | GWh		36,474		36,474
Entergy Mississippi [Member]
Risk Management and Fair Values [Abstract]
Letters of Credit Outstanding, Amount		$ 0.2		$ 0.2		$ 0.2
Total volume of natural gas swaps outstanding (MMBtu) | MMBTU		6,210,000		6,210,000
Total volume of fixed transmission rights outstanding | GWh		10,087		10,087
Entergy New Orleans [Member]
Risk Management and Fair Values [Abstract]
Total volume of natural gas swaps outstanding (MMBtu) | MMBTU		1,256,000		1,256,000
Total volume of fixed transmission rights outstanding | GWh		3,751		3,751
Entergy Texas [Member]
Risk Management and Fair Values [Abstract]
Letters of Credit Outstanding, Amount						4.1
Total volume of fixed transmission rights outstanding | GWh		10,931		10,931
Gas Hedge Contracts [Member] | Entergy Louisiana [Member]
Risk Management and Fair Values [Abstract]
Maximum Length of Time Hedged in Cash Flow Hedge				4 years 6 months
Gas Hedge Contracts [Member] | Entergy Mississippi [Member]
Risk Management and Fair Values [Abstract]
Maximum Length of Time Hedged in Cash Flow Hedge				6 months
Entergy Wholesale Commodities [Member]
Risk Management and Fair Values [Abstract]
Cash collateral posted		$ 13.0		$ 13.0		$ 19.0
Derivative, Collateral, Obligation to Return Cash		2.0		2.0
Letters of Credit Held		$ 48.0		$ 48.0
Number of Derivative Contract Counterparties in a Liability Position | counterparty						6
Dollar amount of hedge contract in a liability position						$ 34.0
Utility [Member]
Risk Management and Fair Values [Abstract]
Letters of Credit Outstanding, Amount						$ 4.0
Subsequent Event [Member]
Risk Management and Fair Values [Abstract]
Planned generation sold forward from non utility nuclear power plants for the remainder of the period	97.00%
Planned Generation From Non Nuclear Power Plants Sold Forward Under Financial Hedges	72.00%
Total planned generation for remainder of the period | TWh	6.1