Decommissioning Trust Funds (Available For Sale Securities Continuous Unrealized Loss Position Fair Value) (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months Fair Value	$ 46.0	$ 130.0
More than 12 months Fair Value	26.0	43.0
Total Fair Value	72.0	173.0
Less than 12 Months Gross Unrealized Losses	2.0	9.0
More than 12 Months Gross Unrealized Losses	2.0	5.0
Total Gross Unrealized Losses	4.0	14.0
Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months Fair Value	234.0	123.0
More than 12 months Fair Value	56.0	60.0
Total Fair Value	290.0	183.0
Less than 12 Months Gross Unrealized Losses	1.0	3.0
More than 12 Months Gross Unrealized Losses	3.0	2.0
Total Gross Unrealized Losses	4.0	5.0
Entergy Arkansas [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months Fair Value		13.7
Total Fair Value		13.7
Less than 12 Months Gross Unrealized Losses		0.4
Total Gross Unrealized Losses		0.4
Entergy Arkansas [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months Fair Value	30.7	14.3
More than 12 months Fair Value	2.0	1.0
Total Fair Value	32.7	15.3
Less than 12 Months Gross Unrealized Losses	0.2	0.4
Total Gross Unrealized Losses	0.2	0.4
Entergy Gulf States Louisiana [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months Fair Value	2.3	14.0
More than 12 months Fair Value	1.5	2.7
Total Fair Value	3.8	16.7
Less than 12 Months Gross Unrealized Losses		0.5
More than 12 Months Gross Unrealized Losses	0.1	0.3
Total Gross Unrealized Losses	0.1	0.8
Entergy Gulf States Louisiana [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months Fair Value	19.7	9.3
More than 12 months Fair Value		1.1
Total Fair Value	19.7	10.4
Less than 12 Months Gross Unrealized Losses	0.1	0.2
More than 12 Months Gross Unrealized Losses		0.1
Total Gross Unrealized Losses	0.1	0.3
Entergy Louisiana [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months Fair Value	4.4	11.6
More than 12 months Fair Value	7.2	10.0
Total Fair Value	11.6	21.6
Less than 12 Months Gross Unrealized Losses		0.3
More than 12 Months Gross Unrealized Losses	0.4	1.3
Total Gross Unrealized Losses	0.4	1.6
Entergy Louisiana [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months Fair Value	3.2	5.5
More than 12 months Fair Value	0.6	0.2
Total Fair Value	3.8	5.7
Less than 12 Months Gross Unrealized Losses	0.1	0.2
Total Gross Unrealized Losses	0.1	0.2
System Energy [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months Fair Value	19.2	41.3
More than 12 months Fair Value	14.7	30.0
Total Fair Value	33.9	71.3
Less than 12 Months Gross Unrealized Losses	0.2	1.8
More than 12 Months Gross Unrealized Losses	0.8	3.6
Total Gross Unrealized Losses	1.0	5.4
System Energy [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months Fair Value	41.8	10.5
More than 12 months Fair Value	0.3
Total Fair Value	42.1	10.5
Less than 12 Months Gross Unrealized Losses	0.1	0.1
Total Gross Unrealized Losses	$ 0.1	$ 0.1