Risk Management and Fair Values (Assets And Liabilities At Fair Value On A Recurring Basis) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013
Assets at fair value on a recurring basis
Assets other than temporary cash investments	$ 5,371.0		$ 4,903.0
Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Temporary cash investments	1,291.0		609.0
Total	7,332.0		5,787.0
Liabilities at fair value on a recurring basis
Total	22
Power Contracts Liabilities [Member] | Fair Value, Measurements, Recurring [Member]
Liabilities at fair value on a recurring basis
Liabilities, Fair Value Disclosure on Recurring Basis	2.0		207.0
Equity Securities [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments	3,286.0	[1]	3,073.0	[1]
Debt Securities [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments	2,085.0	[1]	1,830.0	[1]
Power Contracts Assets [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments	217.0		74.0
Securitization Recovery Trust Account [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments	44.0		46.0
Escrow Accounts [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments	362.0		115.0
Gas Hedge Contracts Assets [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments			6.0
Liabilities at fair value on a recurring basis
Liabilities, Fair Value Disclosure on Recurring Basis	20.0
Fixed Transmission Rights (FTRs) [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments	47.0		34.0
Fair Value Inputs Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Temporary cash investments	1,291.0		609.0
Total	3,029.0		2,031.0
Liabilities at fair value on a recurring basis
Total	20
Fair Value Inputs Level 1 [Member] | Gas Hedge Contracts [Member] | Fair Value, Measurements, Recurring [Member]
Liabilities at fair value on a recurring basis
Liabilities, Fair Value Disclosure on Recurring Basis	20.0
Fair Value Inputs Level 1 [Member] | Equity Securities [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments	452.0	[1]	472.0	[1]
Fair Value Inputs Level 1 [Member] | Debt Securities [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments	880.0	[1]	783.0	[1]
Fair Value Inputs Level 1 [Member] | Securitization Recovery Trust Account [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments	44.0		46.0
Fair Value Inputs Level 1 [Member] | Escrow Accounts [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments	362.0		115.0
Fair Value Inputs Level 1 [Member] | Gas Hedge Contracts Assets [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments			6.0
Fair Value Inputs Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Total	4,039.0		3,648.0
Fair Value Inputs Level 2 [Member] | Equity Securities [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments	2,834.0	[1],[2]	2,601.0	[1],[2]
Fair Value Inputs Level 2 [Member] | Debt Securities [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments	1,205.0	[1]	1,047.0	[1]
Fair Value Inputs Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Total	264.0		108.0
Liabilities at fair value on a recurring basis
Total	2
Fair Value Inputs Level 3 [Member] | Power Contracts Liabilities [Member] | Fair Value, Measurements, Recurring [Member]
Liabilities at fair value on a recurring basis
Liabilities, Fair Value Disclosure on Recurring Basis	2.0		207.0
Fair Value Inputs Level 3 [Member] | Power Contracts Assets [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments	217.0		74.0
Fair Value Inputs Level 3 [Member] | Fixed Transmission Rights (FTRs) [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments	47.0		34.0
Entergy Arkansas [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments	769.9		710.9
Entergy Arkansas [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Temporary cash investments	208.0		122.8
Total	994.9		863.5
Entergy Arkansas [Member] | Equity Securities [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments	487.3	[1]	463.3	[1]
Entergy Arkansas [Member] | Debt Securities [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments	282.6	[1]	247.6	[1]
Entergy Arkansas [Member] | Securitization Recovery Trust Account [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments	4.1		3.8
Entergy Arkansas [Member] | Escrow Accounts [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments	12.2		26.0
Entergy Arkansas [Member] | Fixed Transmission Rights (FTRs) [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments	0.7
Entergy Arkansas [Member] | Fair Value Inputs Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Temporary cash investments	208.0		122.8
Total	303.7		224.8
Entergy Arkansas [Member] | Fair Value Inputs Level 1 [Member] | Equity Securities [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments	7.2	[1]	13.6	[1]
Entergy Arkansas [Member] | Fair Value Inputs Level 1 [Member] | Debt Securities [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments	72.2	[1]	58.6	[1]
Entergy Arkansas [Member] | Fair Value Inputs Level 1 [Member] | Securitization Recovery Trust Account [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments	4.1		3.8
Entergy Arkansas [Member] | Fair Value Inputs Level 1 [Member] | Escrow Accounts [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments	12.2		26.0
Entergy Arkansas [Member] | Fair Value Inputs Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Total	690.5		638.7
Entergy Arkansas [Member] | Fair Value Inputs Level 2 [Member] | Equity Securities [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments	480.1	[1],[2]	449.7	[1],[2]
Entergy Arkansas [Member] | Fair Value Inputs Level 2 [Member] | Debt Securities [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments	210.4	[1]	189.0	[1]
Entergy Arkansas [Member] | Fair Value Inputs Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Total	0.7
Entergy Arkansas [Member] | Fair Value Inputs Level 3 [Member] | Fixed Transmission Rights (FTRs) [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments	0.7
Entergy Gulf States Louisiana [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments	637.7		573.7
Entergy Gulf States Louisiana [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Temporary cash investments	109.6		13.8
Total	851.8		617.9
Entergy Gulf States Louisiana [Member] | Gas Hedge Contracts [Member] | Fair Value, Measurements, Recurring [Member]
Liabilities at fair value on a recurring basis
Liabilities, Fair Value Disclosure on Recurring Basis	8.2
Entergy Gulf States Louisiana [Member] | Equity Securities [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments	395.9	[1]	370.8	[1]
Entergy Gulf States Louisiana [Member] | Debt Securities [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments	241.8	[1]	202.9	[1]
Entergy Gulf States Louisiana [Member] | Escrow Accounts [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments	90.1		21.5
Entergy Gulf States Louisiana [Member] | Gas Hedge Contracts Assets [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments			2.2
Entergy Gulf States Louisiana [Member] | Fixed Transmission Rights (FTRs) [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments	14.4		6.7
Entergy Gulf States Louisiana [Member] | Fair Value Inputs Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Temporary cash investments	109.6		13.8
Total	292.1		136.8
Entergy Gulf States Louisiana [Member] | Fair Value Inputs Level 1 [Member] | Gas Hedge Contracts [Member] | Fair Value, Measurements, Recurring [Member]
Liabilities at fair value on a recurring basis
Liabilities, Fair Value Disclosure on Recurring Basis	8.2
Entergy Gulf States Louisiana [Member] | Fair Value Inputs Level 1 [Member] | Equity Securities [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments	10.5	[1]	27.6	[1]
Entergy Gulf States Louisiana [Member] | Fair Value Inputs Level 1 [Member] | Debt Securities [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments	81.9	[1]	71.7	[1]
Entergy Gulf States Louisiana [Member] | Fair Value Inputs Level 1 [Member] | Escrow Accounts [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments	90.1		21.5
Entergy Gulf States Louisiana [Member] | Fair Value Inputs Level 1 [Member] | Gas Hedge Contracts Assets [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments			2.2
Entergy Gulf States Louisiana [Member] | Fair Value Inputs Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Total	545.3		474.4
Entergy Gulf States Louisiana [Member] | Fair Value Inputs Level 2 [Member] | Equity Securities [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments	385.4	[1],[2]	343.2	[1],[2]
Entergy Gulf States Louisiana [Member] | Fair Value Inputs Level 2 [Member] | Debt Securities [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments	159.9	[1]	131.2	[1]
Entergy Gulf States Louisiana [Member] | Fair Value Inputs Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Total	14.4		6.7
Entergy Gulf States Louisiana [Member] | Fair Value Inputs Level 3 [Member] | Fixed Transmission Rights (FTRs) [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments	14.4		6.7
Entergy Louisiana [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments	383.6		347.3
Entergy Louisiana [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Temporary cash investments	157.1		123.6
Total	755.0		484.0
Entergy Louisiana [Member] | Gas Hedge Contracts [Member] | Fair Value, Measurements, Recurring [Member]
Liabilities at fair value on a recurring basis
Liabilities, Fair Value Disclosure on Recurring Basis	7.6
Entergy Louisiana [Member] | Equity Securities [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments	239.6	[1]	224.2	[1]
Entergy Louisiana [Member] | Debt Securities [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments	144.0	[1]	123.1	[1]
Entergy Louisiana [Member] | Securitization Recovery Trust Account [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments	3.1		4.5
Entergy Louisiana [Member] | Escrow Accounts [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments	200.1
Entergy Louisiana [Member] | Gas Hedge Contracts Assets [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments			2.9
Entergy Louisiana [Member] | Fixed Transmission Rights (FTRs) [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments	11.1		5.7
Entergy Louisiana [Member] | Fair Value Inputs Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Temporary cash investments	157.1		123.6
Total	433.8		206.2
Entergy Louisiana [Member] | Fair Value Inputs Level 1 [Member] | Gas Hedge Contracts [Member] | Fair Value, Measurements, Recurring [Member]
Liabilities at fair value on a recurring basis
Liabilities, Fair Value Disclosure on Recurring Basis	7.6
Entergy Louisiana [Member] | Fair Value Inputs Level 1 [Member] | Equity Securities [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments	4.8	[1]	13.5	[1]
Entergy Louisiana [Member] | Fair Value Inputs Level 1 [Member] | Debt Securities [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments	68.7	[1]	61.7	[1]
Entergy Louisiana [Member] | Fair Value Inputs Level 1 [Member] | Securitization Recovery Trust Account [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments	3.1		4.5
Entergy Louisiana [Member] | Fair Value Inputs Level 1 [Member] | Escrow Accounts [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments	200.1
Entergy Louisiana [Member] | Fair Value Inputs Level 1 [Member] | Gas Hedge Contracts Assets [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments			2.9
Entergy Louisiana [Member] | Fair Value Inputs Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Total	310.1		272.1
Entergy Louisiana [Member] | Fair Value Inputs Level 2 [Member] | Equity Securities [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments	234.8	[1],[2]	210.7	[1],[2]
Entergy Louisiana [Member] | Fair Value Inputs Level 2 [Member] | Debt Securities [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments	75.3	[1]	61.4	[1]
Entergy Louisiana [Member] | Fair Value Inputs Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Total	11.1		5.7
Entergy Louisiana [Member] | Fair Value Inputs Level 3 [Member] | Fixed Transmission Rights (FTRs) [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments	11.1		5.7
Entergy Mississippi [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Temporary cash investments	60.4
Total	105.6		53.5
Entergy Mississippi [Member] | Gas Hedge Contracts [Member] | Fair Value, Measurements, Recurring [Member]
Liabilities at fair value on a recurring basis
Liabilities, Fair Value Disclosure on Recurring Basis	2.8
Entergy Mississippi [Member] | Escrow Accounts [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments	41.8		51.8
Entergy Mississippi [Member] | Gas Hedge Contracts Assets [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments			0.7
Entergy Mississippi [Member] | Fixed Transmission Rights (FTRs) [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments	3.4		1.0
Entergy Mississippi [Member] | Fair Value Inputs Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Temporary cash investments	60.4
Total	102.2		52.5
Entergy Mississippi [Member] | Fair Value Inputs Level 1 [Member] | Gas Hedge Contracts [Member] | Fair Value, Measurements, Recurring [Member]
Liabilities at fair value on a recurring basis
Liabilities, Fair Value Disclosure on Recurring Basis	2.8
Entergy Mississippi [Member] | Fair Value Inputs Level 1 [Member] | Escrow Accounts [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments	41.8		51.8
Entergy Mississippi [Member] | Fair Value Inputs Level 1 [Member] | Gas Hedge Contracts Assets [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments			0.7
Entergy Mississippi [Member] | Fair Value Inputs Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Total	3.4		1.0
Entergy Mississippi [Member] | Fair Value Inputs Level 3 [Member] | Fixed Transmission Rights (FTRs) [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments	3.4		1.0
Entergy New Orleans [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Temporary cash investments	41.4		33.2
Total	63.5		45.8
Entergy New Orleans [Member] | Gas Hedge Contracts [Member] | Fair Value, Measurements, Recurring [Member]
Liabilities at fair value on a recurring basis
Liabilities, Fair Value Disclosure on Recurring Basis	0.9
Entergy New Orleans [Member] | Escrow Accounts [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments	18.0		10.5
Entergy New Orleans [Member] | Gas Hedge Contracts Assets [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments			0.1
Entergy New Orleans [Member] | Fixed Transmission Rights (FTRs) [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments	4.1		2.0
Entergy New Orleans [Member] | Fair Value Inputs Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Temporary cash investments	41.4		33.2
Total	59.4		43.8
Entergy New Orleans [Member] | Fair Value Inputs Level 1 [Member] | Gas Hedge Contracts [Member] | Fair Value, Measurements, Recurring [Member]
Liabilities at fair value on a recurring basis
Liabilities, Fair Value Disclosure on Recurring Basis	0.9
Entergy New Orleans [Member] | Fair Value Inputs Level 1 [Member] | Escrow Accounts [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments	18.0		10.5
Entergy New Orleans [Member] | Fair Value Inputs Level 1 [Member] | Gas Hedge Contracts Assets [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments			0.1
Entergy New Orleans [Member] | Fair Value Inputs Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Total	4.1		2.0
Entergy New Orleans [Member] | Fair Value Inputs Level 3 [Member] | Fixed Transmission Rights (FTRs) [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments	4.1		2.0
Entergy Texas [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Temporary cash investments	28.7		44.1
Total	78.2		100.0
Entergy Texas [Member] | Securitization Recovery Trust Account [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments	37.2		37.5
Entergy Texas [Member] | Fixed Transmission Rights (FTRs) [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments	12.3		18.4
Entergy Texas [Member] | Fair Value Inputs Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Temporary cash investments	28.7		44.1
Total	65.9		81.6
Entergy Texas [Member] | Fair Value Inputs Level 1 [Member] | Securitization Recovery Trust Account [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments	37.2		37.5
Entergy Texas [Member] | Fair Value Inputs Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Total	12.3		18.4
Entergy Texas [Member] | Fair Value Inputs Level 3 [Member] | Fixed Transmission Rights (FTRs) [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments	12.3		18.4
System Energy [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments	679.8		603.9
System Energy [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Temporary cash investments	222.4		64.6
Total	902.2		668.5
System Energy [Member] | Equity Securities [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments	424.5	[1]	380.0	[1]
System Energy [Member] | Debt Securities [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments	255.3	[1]	223.9	[1]
System Energy [Member] | Fair Value Inputs Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Temporary cash investments	222.4		64.6
Total	418.6		219.7
System Energy [Member] | Fair Value Inputs Level 1 [Member] | Equity Securities [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments	2.0	[1]	2.2	[1]
System Energy [Member] | Fair Value Inputs Level 1 [Member] | Debt Securities [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments	194.2	[1]	152.9	[1]
System Energy [Member] | Fair Value Inputs Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Total	483.6		448.8
System Energy [Member] | Fair Value Inputs Level 2 [Member] | Equity Securities [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments	422.5	[1],[2]	377.8	[1],[2]
System Energy [Member] | Fair Value Inputs Level 2 [Member] | Debt Securities [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments	$ 61.1	[1]	$ 71.0	[1]

[1] The decommissioning trust funds hold equity and fixed income securities. Equity securities are invested to approximate the returns of major market indices. Fixed income securities are held in various governmental and corporate securities. See Note 17 to the financial statements for additional information on the investment portfolios.

[2] (b)Commingled equity funds may be redeemed semi-monthly.