Taxes (Details 1) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Reconciliation of federal income tax expense at the federal statutory rate to the total provision for income taxes
Income from Continuing Operations, before income taxes									$ 1,512	$ 1,426	$ 1,078
Federal income tax expense at statutory rate (21%, 35%, and 35% for 2018, 2017, and 2016, respectively)									318	499	377
Increases (reductions) in taxes resulting from-
State income taxes, net of federal tax benefit									90	40	16
AFUDC equity and other flow-through									(31)	(15)	(13)
Amortization of investment tax credits									(5)	(6)	(6)
ESOP dividend									(3)	(5)	(4)
Remeasurement of deferred taxes									24	1,193	0
WV unitary group remeasurement									126	0	0
Excess deferred tax amortization due to the Tax Act									(60)	0	0
Uncertain tax positions									2	(3)	(8)
Valuation allowances									21	11	160
Other, net									8	1	5
Total income taxes	$ (13)	$ 133	$ 121	$ 249	$ 1,232	$ 202	$ 132	$ 149	$ 490	$ 1,715	$ 527
Effective income tax rate (percent)									32.40%	120.30%	49.00%