Decommissioning Trust Funds (Narrative) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2015 USD ($) counterparty	Dec. 31, 2014 USD ($) counterparty	Dec. 31, 2013 USD ($)
Number of Hedge Contracts Counterparties | counterparty	2	1
Decommissioning Trust Funds [Abstract]
Deferred taxes on unrealized gains/(losses) recorded in OCI for non-regulated decommissioning trusts	$ 342.0	$ 396.0
Amortized cost of debt securities	$ 2,124.0	2,019.0
Average coupon rate of debt securities	3.16%
Proceeds from the dispositions of debt securities	$ 2,492.0	1,872.0	$ 2,032.0
Gains from dispositions of debt securities, gross	72.0	39.0	91.0
Losses from dispositions of debt securities, gross	$ 13.0	8.0	11.0
Average Duration of Debt Securities in Years	5 years 8 months 13 days
Average Maturity of Debt Securities, Years	8 years 6 months 20 days
Hedge Contracts In Liability Position	$ 2.0	1.0
Cash Collateral Requirement	68.0	25.0
Entergy Arkansas [Member]
Decommissioning Trust Funds [Abstract]
Amortized cost of debt securities	$ 301.8	277.4
Average coupon rate of debt securities	2.44%
Proceeds from the dispositions of debt securities	$ 213.0	181.5	266.4
Gains from dispositions of debt securities, gross	5.9	8.7	16.8
Losses from dispositions of debt securities, gross	$ 0.3	0.3	0.6
Average Duration of Debt Securities in Years	5 years 1 month 20 days
Average Maturity of Debt Securities, Years	5 years 11 months 24 days
Entergy Louisiana [Member]
Percentage Interest in River Bend	30.00%
Decommissioning Trust Funds [Abstract]
Amortized cost of debt securities	$ 399.2	369.4
Average coupon rate of debt securities	3.89%
Proceeds from the dispositions of debt securities	$ 123.5	216.7	303.7
Gains from dispositions of debt securities, gross	1.9	2.2	22.0
Losses from dispositions of debt securities, gross	$ 0.3	0.3	0.2
Average Duration of Debt Securities in Years	5 years 5 months 28 days
Average Maturity of Debt Securities, Years	9 years 10 months 28 days
System Energy [Member]
Decommissioning Trust Funds [Abstract]
Amortized cost of debt securities	$ 270.7	251.0
Average coupon rate of debt securities	2.16%
Proceeds from the dispositions of debt securities	$ 390.4	392.9	215.5
Gains from dispositions of debt securities, gross	3.3	1.8	1.5
Losses from dispositions of debt securities, gross	$ 0.5	$ 0.9	$ 1.3
Average Duration of Debt Securities in Years	4 years 10 months 10 days
Average Maturity of Debt Securities, Years	6 years 4 months 4 days