Commitments and Contingencies (Schedule of Environmental Loss Contingencies) (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Accrual for Environmental Loss Contingencies [Roll Forward]
Balance at beginning of period	$ 77	$ 81
Provisions/adjustments	30	7
Cash reductions	(35)	(20)
Balance at end of period	72	68
Environmental exit costs, reasonably possible additional loss	49
Duke Energy Carolinas [Member]
Accrual for Environmental Loss Contingencies [Roll Forward]
Balance at beginning of period	11	10
Provisions/adjustments	4	3
Cash reductions	(4)	(2)
Balance at end of period	11	11
Environmental exit costs, reasonably possible additional loss	11
Progress Energy [Member]
Accrual for Environmental Loss Contingencies [Roll Forward]
Balance at beginning of period	11	15
Provisions/adjustments	9	2
Cash reductions	(3)	(5)
Balance at end of period	17	12
Duke Energy Progress [Member]
Accrual for Environmental Loss Contingencies [Roll Forward]
Balance at beginning of period	4	3
Provisions/adjustments	3	3
Cash reductions	(2)	(1)
Balance at end of period	5	5
Duke Energy Florida [Member]
Accrual for Environmental Loss Contingencies [Roll Forward]
Balance at beginning of period	6	12
Provisions/adjustments	5	(1)
Cash reductions	(1)	(4)
Balance at end of period	10	7
Duke Energy Ohio [Member]
Accrual for Environmental Loss Contingencies [Roll Forward]
Balance at beginning of period	48	47
Provisions/adjustments	10	3
Cash reductions	(28)	(12)
Balance at end of period	30	38
Environmental exit costs, reasonably possible additional loss	31
Duke Energy Indiana [Member]
Accrual for Environmental Loss Contingencies [Roll Forward]
Balance at beginning of period	5	5
Provisions/adjustments		1
Cash reductions	0	(1)
Balance at end of period	5	5
Piedmont Natural Gas [Member]
Accrual for Environmental Loss Contingencies [Roll Forward]
Balance at beginning of period	2	2
Provisions/adjustments	6
Cash reductions	0
Balance at end of period	8	$ 2
Environmental exit costs, reasonably possible additional loss	$ 2