Decommissioning Trust Funds (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Decommissioning Trust Funds [Abstract]
Deferred taxes on unrealized gains/(losses) recorded in OCI for non-regulated decommissioning trusts			$ 380.0		$ 342.0
Amortized cost of debt securities	$ 2,189.0		$ 2,189.0		2,124.0
Average coupon rate of debt securities	3.20%		3.20%
Average duration of debt securities, years			5 years 9 months 30 days
Average maturity of debt securities, years			9 years 2 months 21 days
Proceeds from the dispositions of debt securities	$ 504.0	$ 456.0	$ 1,233.0	$ 949.0
Gains from dispositions of debt securities, gross	10.0	19.0	20.0	45.0
Losses from dispositions of debt securities, gross	2.0	1.0	5.0	3.0
Entergy Arkansas [Member]
Decommissioning Trust Funds [Abstract]
Amortized cost of debt securities	$ 299.5		$ 299.5		301.8
Average coupon rate of debt securities	2.61%		2.61%
Average duration of debt securities, years			5 years 2 months 10 days
Average maturity of debt securities, years			5 years 11 months 9 days
Proceeds from the dispositions of debt securities	$ 45.2	64.9	$ 103.8	146.8
Gains from dispositions of debt securities, gross	0.4	0.3	1.2	5.4
Losses from dispositions of debt securities, gross	0.2	0.0	$ 0.3	0.0
Entergy Louisiana [Member]
Decommissioning Trust Funds [Abstract]
Percentage Interest in River Bend			30.00%
Amortized cost of debt securities	$ 413.4		$ 413.4		399.2
Average coupon rate of debt securities	3.85%		3.85%
Average duration of debt securities, years			5 years 5 months 21 days
Average maturity of debt securities, years			11 years 2 months 10 days
Proceeds from the dispositions of debt securities	$ 69.7	39.6	$ 123.5	65.2
Gains from dispositions of debt securities, gross	1.7	0.2	2.6	1.5
Losses from dispositions of debt securities, gross	0.0	0.2	0.1	0.2
System Energy [Member]
Decommissioning Trust Funds [Abstract]
Amortized cost of debt securities	$ 295.2		$ 295.2		$ 270.7
Average coupon rate of debt securities	1.87%		1.87%
Average duration of debt securities, years			5 years 2 months 13 days
Average maturity of debt securities, years			6 years 4 months 7 days
Proceeds from the dispositions of debt securities	$ 100.9	83.6	$ 289.4	162.0
Gains from dispositions of debt securities, gross	0.9	0.4	2.5	0.8
Losses from dispositions of debt securities, gross	$ 0.1	$ 0.0	$ 0.4	$ 0.1