Income Taxes Income Taxes (Narrative) (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended
	Jun. 30, 2018	Jun. 30, 2018	Dec. 31, 2017
Entergy Arkansas [Member]
Reduction to regulatory liability for income taxes resulting from return of unprotected excess ADIT		$ 108
Entergy Louisiana [Member]
Tax benefits related to Hurricane Katrina and Hurricane Rita contingent sharing obligation	$ 52
Unrecognized Tax Benefits	$ 856	856	$ 926
Reduction to regulatory liability for income taxes resulting from return of unprotected excess ADIT		31
Entergy Mississippi [Member]
Reduction to regulatory liability for income taxes resulting from return of unprotected excess ADIT		129
System Energy [Member]
Reduction to regulatory liability for income taxes resulting from return of unprotected excess ADIT		$ 11