Decommissioning Trust Funds (Securities Held) (Details) - Debt Securities [Member] - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Fair Value	$ 2,581.0	$ 2,456.0
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	201.0	96.0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	2.0	6.0
Entergy Arkansas [Member]
Debt Securities, Available-for-sale [Line Items]
Fair Value	433.2	412.8
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	29.5	9.9
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	0.2	2.6
Entergy Louisiana [Member]
Debt Securities, Available-for-sale [Line Items]
Fair Value	626.4	601.5
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	50.5	29.3
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	0.5	0.8
System Energy [Member]
Debt Securities, Available-for-sale [Line Items]
Fair Value	420.8	386.2
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	31.6	15.1
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	$ 0.4	$ 0.3

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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- Definition

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

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27161-111563

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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.

+ References

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+ References

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