Taxes (Details 1) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Reconciliation of federal income tax expense at the federal statutory rate to the total provision for income taxes
Income (loss) from Continuing Operations before income taxes (benefits)									$ (9,232)	$ 893	$ 171
Federal income tax expense (benefit) at statutory rate (35%)									(3,231)	313	60
Increases (reductions) in taxes resulting from-
State income taxes, net of federal tax benefit									(192)	17	(21)
AFUDC equity and other flow-through									(13)	(16)	(13)
Amortization of investment tax credits									(8)	(8)	(10)
Change in accounting method									0	(8)	(27)
ESOP dividend									(6)	(6)	(6)
Impairment of non-deductible goodwill									157	0	0
Tax basis balance sheet adjustments									0	0	(25)
Uncertain tax positions									(16)	1	(35)
Valuation allowances									246	18	33
Other, net									8	4	2
Total provision for income taxes (benefits)	$ (3,389)	$ 251	$ (130)	$ 213	$ (170)	$ 226	$ 115	$ 144	$ (3,055)	$ 315	$ (42)
Effective income tax rate (percent)									33.10%	35.30%	(24.60%)
FES
Reconciliation of federal income tax expense at the federal statutory rate to the total provision for income taxes
Income (loss) from Continuing Operations before income taxes (benefits)									$ (8,444)	$ 147	$ (588)
Federal income tax expense (benefit) at statutory rate (35%)									(2,955)	51	(206)
Increases (reductions) in taxes resulting from-
State income taxes, net of federal tax benefit									(188)	2	(28)
Amortization of investment tax credits									(2)	(2)	(4)
ESOP dividend									(1)	(1)	(1)
Impairment of non-deductible goodwill									9	0	0
Uncertain tax positions									(8)	5	0
Valuation allowances									151	14	14
Other, net									6	(4)	(3)
Total provision for income taxes (benefits)	$ (2,983)	$ 56	$ (143)	$ 82	$ 1	$ 70	$ (4)	$ (2)	$ (2,988)	$ 65	$ (228)
Effective income tax rate (percent)									35.40%	44.20%	38.80%