Commitments and Contingencies (Schedule of Environmental Loss Contingencies) (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Environmental Matters Details [Line Items]
Environmental Exit Costs, Reasonably Possible Additional Loss	$ 55
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	81	$ 98
Provisions/adjustments	1
Cash reductions	(14)	(8)
Ending balance	68	90
Duke Energy Carolinas [Member]
Environmental Matters Details [Line Items]
Environmental Exit Costs, Reasonably Possible Additional Loss	16
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	10	10
Provisions/adjustments	2	1
Cash reductions	(1)	(1)
Ending balance	11	10
Progress Energy [Member]
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	15	18
Provisions/adjustments	2
Cash reductions	(2)	(2)
Ending balance	15	16
Duke Energy Progress [Member]
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	3	3
Provisions/adjustments	2
Cash reductions	(1)
Ending balance	4	3
Duke Energy Florida [Member]
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	12	14
Provisions/adjustments	(1)	1
Cash reductions	(1)	(2)
Ending balance	10	13
Duke Energy Ohio [Member]
Environmental Matters Details [Line Items]
Environmental Exit Costs, Reasonably Possible Additional Loss	30
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	47	59
Provisions/adjustments	(3)	(2)
Cash reductions	(9)	(4)
Ending balance	35	53
Duke Energy Indiana [Member]
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	5	10
Provisions/adjustments	1
Cash reductions	(1)	(1)
Ending balance	5	9
Piedmont Natural Gas [Member]
Environmental Matters Details [Line Items]
Environmental Exit Costs, Reasonably Possible Additional Loss	2
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	2	1
Cash reductions	0
Ending balance	$ 2	$ 1