Decommissioning Trust Funds (Securities Held) (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Trading, Measurement Input	$ 521.0	$ 507.0
Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Fair Value	2,523.0	2,456.0
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	158.0	96.0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	16.0	6.0
Entergy Arkansas [Member] \| Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Fair Value	417.8	412.8
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	20.4	9.9
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	1.4	2.6
Entergy Louisiana [Member] \| Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Fair Value	603.0	601.5
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	38.5	29.3
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	3.9	0.8
System Energy [Member] \| Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Fair Value	408.0	386.2
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	26.9	15.1
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	$ 2.7	$ 0.3

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Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

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Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

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Amount of investment in debt security measured at fair value with change in fair value recognized in net income (trading).

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
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