Commitments and Contingencies (Schedule of Environmental Loss Contingencies) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Environmental Matters Details [Line Items]
Environmental Exit Costs, Reasonably Possible Additional Loss	$ 57
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	81	$ 98
Provisions/adjustments	4	6
Cash reductions	(5)	(6)
Ending balance	80	98
Duke Energy Carolinas [Member]
Environmental Matters Details [Line Items]
Environmental Exit Costs, Reasonably Possible Additional Loss	19
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	10	10
Provisions/adjustments	1	1
Cash reductions	0
Ending balance	11	11
Progress Energy [Member]
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	15	18
Provisions/adjustments	3
Cash reductions	(2)	(1)
Ending balance	16	17
Duke Energy Progress [Member]
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	3	3
Provisions/adjustments	1
Cash reductions	(1)
Ending balance	3	3
Duke Energy Florida [Member]
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	12	14
Provisions/adjustments	1	1
Cash reductions	(1)	(1)
Ending balance	12	14
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		4
Cash reductions	(3)	(4)
Ending balance	44	59
Duke Energy Indiana [Member]
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	5	10
Provisions/adjustments	1	(1)
Cash reductions	0
Ending balance	6	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
Provisions/adjustments		1
Cash reductions	0
Ending balance	$ 2	$ 2