Risk Management and Fair Values (Assets And Liabilities At Fair Value On A Recurring Basis) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013		Dec. 31, 2012
Assets at fair value on a recurring basis
Assets other than temporary cash investments	$ 4,903.0		$ 4,190.0
Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Temporary cash investments	609.0		420.0
Total	5,787.0		5,233.0
Liabilities at fair value on a recurring basis
Total			21
Gas Hedge Contracts [Member] | Fair Value, Measurements, Recurring [Member]
Liabilities at fair value on a recurring basis
Liabilities, Fair Value Disclosure on Recurring Basis			8.0
Power Contracts Liabilities [Member] | Fair Value, Measurements, Recurring [Member]
Liabilities at fair value on a recurring basis
Liabilities, Fair Value Disclosure on Recurring Basis	207.0		13.0
Equity Securities [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments	3,073.0	[1]	2,459.0	[1]
Debt Securities [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments	1,830.0	[1]	1,731.0	[1]
Power Contracts Assets [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments	74.0		191.0
Securitization Recovery Trust Account [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments	46.0		46.0
Escrow Accounts [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments	115.0		386.0
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
Fixed Transmission Rights (FTRs) [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments	34.0
Fair Value Inputs Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Temporary cash investments	609.0		420.0
Total	2,031.0		1,979.0
Liabilities at fair value on a recurring basis
Total			8
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			8.0
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	472.0	[1]	358.0	[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	783.0	[1]	769.0	[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	46.0		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	115.0		386.0
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	3,648.0		3,063.0
Liabilities at fair value on a recurring basis
Total			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	2,601.0	[1]	2,101.0	[1]
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	1,047.0	[1]	962.0	[1]
Fair Value Inputs Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Total	108.0		191.0
Liabilities at fair value on a recurring basis
Total			13
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	207.0		13.0
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	74.0		191.0
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	34.0
Entergy Arkansas [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments	710.9		600.6
Entergy Arkansas [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Temporary cash investments	122.8		24.9
Total	863.5		667.9
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	463.3		384.0
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	247.6		216.6
Entergy Arkansas [Member] | Securitization Recovery Trust Account [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments			4.4
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	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	26.0		38.0
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	122.8		24.9
Total	224.8		171.1
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	13.6		9.5
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	58.6		94.3
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	3.8		4.4
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	26.0		38.0
Entergy Arkansas [Member] | Fair Value Inputs Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Total	638.7		496.8
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	449.7		374.5
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	189.0		122.3
Entergy Gulf States Louisiana [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments	573.7		477.4
Entergy Gulf States Louisiana [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Temporary cash investments	13.8		0.6
Total	617.9		565.0
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			2.6
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	370.8		288.5
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	202.9		188.9
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	21.5		87.0
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	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	13.8		0.6
Total	136.8		142.6
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			2.6
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	27.6		5.5
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	71.7		49.5
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	21.5		87.0
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	474.4		422.4
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	343.2		283.0
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	131.2		139.4
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	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	6.7
Entergy Louisiana [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments	347.3		287.4
Entergy Louisiana [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Temporary cash investments	123.6		29.3
Total	484.0		508.1
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			3.4
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	224.2		175.5
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	123.1		111.9
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	4.5		4.4
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			187.0
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	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	123.6		29.3
Total	206.2		275.3
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			3.4
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	13.5		2.0
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	61.7		52.6
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	4.5		4.4
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			187.0
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	272.1		232.8
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	210.7		173.5
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	61.4		59.3
Entergy Louisiana [Member] | Fair Value Inputs Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Total	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	5.7
Entergy Mississippi [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Temporary cash investments			52.4
Total	53.5		114.2
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			2.2
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	51.8		61.8
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	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			52.4
Total	52.5		114.2
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			2.2
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	51.8		61.8
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
Assets other than temporary cash investments	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	1.0
Entergy New Orleans [Member]
Assets at fair value on a recurring basis
Temporary cash investments	33.2
Total	45.8
Entergy New Orleans [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Temporary cash investments			9.1
Total			19.7
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	10.5		10.6
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	2.0
Entergy New Orleans [Member] | Fair Value Inputs Level 1 [Member]
Assets at fair value on a recurring basis
Temporary cash investments	33.2
Total	43.8
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			9.1
Total			19.7
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	10.5		10.6
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
Assets other than temporary cash investments	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	2.0
Entergy Texas [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Temporary cash investments	44.1		59.7
Total	100.0		97.0
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	37.5		37.3
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	44.1		59.7
Total	81.6		97.0
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	37.5		37.3
Entergy Texas [Member] | Fair Value Inputs Level 1 [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	18.4
Entergy Texas [Member] | Fair Value Inputs Level 3 [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	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	18.4
System Energy [Member]
Assets at fair value on a recurring basis
Assets other than temporary cash investments	603.9		490.6
System Energy [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Temporary cash investments	64.6
Total	668.5		574.1
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	380.0		283.6	[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	223.9		207.0	[1]
System Energy [Member] | Other Aggregated Investments [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Temporary cash investments			83.5
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	64.6
Total	219.7		226.2
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	2.2		1.6	[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	152.9		141.1	[1]
System Energy [Member] | Fair Value Inputs Level 1 [Member] | Other Aggregated Investments [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Temporary cash investments			83.5
System Energy [Member] | Fair Value Inputs Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Assets at fair value on a recurring basis
Total	448.8		347.9
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	377.8		282.0	[1]
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	$ 71.0		$ 65.9	[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 for additional information on the investment portfolios.