Commitments and Contingencies (Schedule of Environmental Loss Contingencies) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Accrual for Environmental Loss Contingencies [Roll Forward]
Balance at beginning of period	$ 77	$ 81
Provisions/adjustments	(2)	4
Cash reductions	(8)	(5)
Balance at end of period	67	80
Environmental exit costs, reasonably possible additional loss	45
Duke Energy Carolinas [Member]
Accrual for Environmental Loss Contingencies [Roll Forward]
Balance at beginning of period	11	10
Provisions/adjustments	2	1
Cash reductions	0
Balance at end of period	13	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	2	3
Cash reductions		(2)
Balance at end of period	13	16
Duke Energy Progress [Member]
Accrual for Environmental Loss Contingencies [Roll Forward]
Balance at beginning of period	4	3
Provisions/adjustments	1	1
Cash reductions	0	(1)
Balance at end of period	5	3
Duke Energy Florida [Member]
Accrual for Environmental Loss Contingencies [Roll Forward]
Balance at beginning of period	6	12
Provisions/adjustments	2	1
Cash reductions	0	(1)
Balance at end of period	8	12
Duke Energy Ohio [Member]
Accrual for Environmental Loss Contingencies [Roll Forward]
Balance at beginning of period	48	47
Provisions/adjustments	(6)
Cash reductions	(8)	(3)
Balance at end of period	34	44
Environmental exit costs, reasonably possible additional loss	22
Duke Energy Indiana [Member]
Accrual for Environmental Loss Contingencies [Roll Forward]
Balance at beginning of period	5	5
Provisions/adjustments		1
Cash reductions	0
Balance at end of period	5	6
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