Commitments and Contingencies (Schedule of Environmental Loss Contingencies) (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Accrual for Environmental Loss Contingencies [Roll Forward]
Balance at beginning of period	$ 77	$ 81
Provisions/adjustments	9	1
Cash reductions	(22)	(14)
Balance at end of period	64	68
Environmental exit costs, reasonably possible additional loss	51
Duke Energy Carolinas [Member]
Accrual for Environmental Loss Contingencies [Roll Forward]
Balance at beginning of period	11	10
Provisions/adjustments	4	2
Cash reductions	(3)	(1)
Balance at end of period	12	11
Environmental exit costs, reasonably possible additional loss	12
Progress Energy [Member]
Accrual for Environmental Loss Contingencies [Roll Forward]
Balance at beginning of period	11	15
Provisions/adjustments	3	2
Cash reductions	(1)	(2)
Balance at end of period	13	15
Duke Energy Progress [Member]
Accrual for Environmental Loss Contingencies [Roll Forward]
Balance at beginning of period	4	3
Provisions/adjustments	2	2
Cash reductions	(1)	(1)
Balance at end of period	5	4
Duke Energy Florida [Member]
Accrual for Environmental Loss Contingencies [Roll Forward]
Balance at beginning of period	6	12
Provisions/adjustments	1	(1)
Cash reductions	0	(1)
Balance at end of period	7	10
Duke Energy Ohio [Member]
Accrual for Environmental Loss Contingencies [Roll Forward]
Balance at beginning of period	48	47
Provisions/adjustments	2	(3)
Cash reductions	(18)	(9)
Balance at end of period	32	35
Environmental exit costs, reasonably possible additional loss	29
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
Cash reductions	0
Balance at end of period	2	$ 2
Environmental exit costs, reasonably possible additional loss	$ 2