Decommissioning Trust Funds (Securities Held) (Details) - Debt Securities [Member] - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Debt Securities, Available-for-sale [Line Items]
Fair Value	$ 3,436.0	$ 2,617.0
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	102.0	197.0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	43.0	3.0
Entergy Arkansas [Member]
Debt Securities, Available-for-sale [Line Items]
Fair Value	425.9	447.9
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	13.2	27.7
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	6.8	0.3
Entergy Louisiana [Member]
Debt Securities, Available-for-sale [Line Items]
Fair Value	632.8	632.2
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	31.2	51.3
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	4.6	0.5
System Energy [Member]
Debt Securities, Available-for-sale [Line Items]
Fair Value	406.4	427.7
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	14.3	30.0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	$ 5.0	$ 0.8

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=121645371&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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