Taxes (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Currently payable (receivable)-
Federal									$ 14	$ (1)	$ 1
State									42	9	30
Currently payable (receivable) Total									56	8	31
Deferred, net-
Federal									876	(3,114)	277
State									(29)	59	15
Deferred Tax Total									847	(3,055)	292
Investment tax credit amortization									(8)	(8)	(8)
Total provision for income taxes (benefits)	$ 413	$ 239	$ 117	$ 126	$ (3,389)	$ 251	$ (130)	$ 213	895	(3,055)	315
FES
Currently payable (receivable)-
Federal									(159)	(67)	(56)
State									(1)	(1)	2
Currently payable (receivable) Total									(160)	(68)	(54)
Deferred, net-
Federal									509	(2,861)	103
State									(52)	(57)	18
Deferred Tax Total									457	(2,918)	121
Investment tax credit amortization									(2)	(2)	(2)
Total provision for income taxes (benefits)	$ 281	$ 32	$ 23	$ (41)	$ (2,983)	$ 56	$ (143)	$ 82	$ 295	$ (2,988)	$ 65