Commitments and Contingencies (Schedule of Environmental Loss Contingencies) (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Environmental Matters Details [Line Items]
Environmental Exit Costs, Reasonably Possible Additional Loss	$ 70
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	98	$ 94
Provisions/adjustments		27
Cash reductions	(8)	(7)
Ending balance	90	114
Duke Energy Carolinas [Member]
Environmental Matters Details [Line Items]
Environmental Exit Costs, Reasonably Possible Additional Loss	23
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	10	10
Provisions/adjustments	1	3
Cash reductions	(1)	(2)
Ending balance	10	11
Progress Energy [Member]
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	18	17
Provisions/adjustments		4
Cash reductions	(2)	(4)
Ending balance	16	17
Duke Energy Progress [Member]
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	3	3
Provisions/adjustments		1
Cash reductions	0	(1)
Ending balance	3	3
Duke Energy Florida [Member]
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	14	14
Provisions/adjustments	1	3
Cash reductions	(2)	(3)
Ending balance	13	14
Duke Energy Ohio [Member]
Environmental Matters Details [Line Items]
Environmental Exit Costs, Reasonably Possible Additional Loss	35
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	59	54
Provisions/adjustments	(2)	1
Cash reductions	(4)	(1)
Ending balance	53	54
Duke Energy Indiana [Member]
Environmental Matters Details [Line Items]
Environmental Exit Costs, Reasonably Possible Additional Loss	7
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	10	12
Provisions/adjustments		21
Cash reductions	(1)	(1)
Ending balance	9	32
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	1	1
Cash reductions	0
Ending balance	$ 1	$ 1