Commitments and Contingencies (Schedule of Environmental Loss Contingencies) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Oct. 31, 2016	Oct. 31, 2015
Disclosure Environmental Matters Details [Line Items]
Environmental reserve	$ 81	$ 98	$ 94
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	81	98	94
Provision/adjustments	26	8	19
Cash reductions	(30)	(25)	(15)
Ending balance	77	81	98
Duke Energy Carolinas [Member]
Disclosure Environmental Matters Details [Line Items]
Environmental reserve	10	10	10
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	10	10	10
Provision/adjustments	3	3	4
Cash reductions	(2)	(3)	(4)
Ending balance	11	10	10
Progress Energy [Member]
Disclosure Environmental Matters Details [Line Items]
Environmental reserve	15	18	17
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	15	18	17
Provision/adjustments	2	3	7
Cash reductions	(6)	(6)	(6)
Ending balance	11	15	18
Duke Energy Progress [Member]
Disclosure Environmental Matters Details [Line Items]
Environmental reserve	3	3	3
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	3	3	3
Provision/adjustments	3	2	2
Cash reductions	(2)	(2)	(2)
Ending balance	4	3	3
Duke Energy Florida [Member]
Disclosure Environmental Matters Details [Line Items]
Environmental reserve	12	14	14
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	12	14	14
Provision/adjustments	(2)	2	4
Cash reductions	(4)	(4)	(4)
Ending balance	6	12	14
Duke Energy Ohio [Member]
Disclosure Environmental Matters Details [Line Items]
Environmental reserve	47	59	54
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	47	59	54
Provision/adjustments	21	3	7
Cash reductions	(20)	(15)	(2)
Ending balance	48	47	59
Duke Energy Indiana [Member]
Disclosure Environmental Matters Details [Line Items]
Environmental reserve	5	10	12
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	5	10	12
Provision/adjustments	1	(4)	1
Cash reductions	(1)	(1)	(3)
Ending balance	5	5	10
Piedmont Natural Gas [Member]
Disclosure Environmental Matters Details [Line Items]
Environmental reserve	2	1	1	$ 1	$ 1
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	2	1
Ending balance	2	$ 2	$ 1
Environmental Reserves [Member]
Disclosure Environmental Matters Details [Line Items]
Environmental Exit Costs, Reasonably Possible Additional Loss	46
Environmental Reserves [Member] | Duke Energy Carolinas [Member]
Disclosure Environmental Matters Details [Line Items]
Environmental Exit Costs, Reasonably Possible Additional Loss	17
Environmental Reserves [Member] | Duke Energy Ohio [Member]
Disclosure Environmental Matters Details [Line Items]
Environmental Exit Costs, Reasonably Possible Additional Loss	19
Environmental Reserves [Member] | Piedmont Natural Gas [Member]
Disclosure Environmental Matters Details [Line Items]
Environmental Exit Costs, Reasonably Possible Additional Loss	$ 2