Commitments and Contingencies (Schedule of Environmental Loss Contingencies) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Environmental Matters Details [Line Items]
Environmental Exit Costs, Reasonably Possible Additional Loss	$ 71
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	98	$ 94
Provisions/adjustments	6	10
Cash reductions	(6)	(3)
Ending balance	98	101
Duke Energy Carolinas [Member]
Environmental Matters Details [Line Items]
Environmental Exit Costs, Reasonably Possible Additional Loss	22
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	10	10
Provisions/adjustments	1	2
Cash reductions	0	(1)
Ending balance	11	11
Progress Energy [Member]
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	18	17
Provisions/adjustments		1
Cash reductions	(1)	(2)
Ending balance	17	16
Duke Energy Progress [Member]
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	3	3
Cash reductions	0	(1)
Ending balance	3	2
Duke Energy Florida [Member]
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	14	14
Provisions/adjustments	1	1
Cash reductions	(1)	(1)
Ending balance	14	14
Duke Energy Ohio [Member]
Environmental Matters Details [Line Items]
Environmental Exit Costs, Reasonably Possible Additional Loss	36
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	59	54
Provisions/adjustments	4
Cash reductions	(4)
Ending balance	59	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	(1)	6
Cash reductions	0
Ending balance	9	18
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
Provisions/adjustments	1
Cash reductions	0
Ending balance	$ 2	$ 1