Commitments and Contingencies (Schedule of Environmental Loss Contingencies)(Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Oct. 31, 2016	Dec. 31, 2015	Oct. 31, 2015	Oct. 31, 2014
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	$ 98	$ 94		$ 92
Provision/adjustments	8	19		11
Cash reductions	(25)	(15)		(9)
Ending balance	81	98		94
Duke Energy Carolinas [Member]
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	10	10		10
Provision/adjustments	3	4		1
Cash reductions	(3)	(4)		(1)
Ending balance	10	10		10
Progress Energy [Member]
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	18	17		17
Provision/adjustments	3	7		4
Cash reductions	(6)	(6)		(4)
Ending balance	15	18		17
Duke Energy Progress [Member]
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	3	3		5
Provision/adjustments	2	2
Cash reductions	(2)	(2)		(2)
Ending balance	3	3		3
Duke Energy Florida [Member]
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	14	14		12
Provision/adjustments	2	4		4
Cash reductions	(4)	(4)		(2)
Ending balance	12	14		14
Duke Energy Ohio [Member]
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	59	54		54
Provision/adjustments	3	7		1
Cash reductions	(15)	(2)		(1)
Ending balance	47	59		54
Duke Energy Indiana [Member]
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	10	12		10
Provision/adjustments	(4)	1		5
Cash reductions	(1)	(3)		(3)
Ending balance	5	10		$ 12
Piedmont Natural Gas [Member]
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	1		$ 1		$ 1
Provision/adjustments	1		0		0	$ 0
Ending balance	2	$ 1	$ 1		$ 1	$ 1
Environmental Reserves [Member]
Disclosure Environmental Matters Details [Line Items]
Environmental Exit Costs, Reasonably Possible Additional Loss	56
Environmental Reserves [Member] | Duke Energy Carolinas [Member]
Disclosure Environmental Matters Details [Line Items]
Environmental Exit Costs, Reasonably Possible Additional Loss	19
Environmental Reserves [Member] | Duke Energy Ohio [Member]
Disclosure Environmental Matters Details [Line Items]
Environmental Exit Costs, Reasonably Possible Additional Loss	30
Environmental Reserves [Member] | Piedmont Natural Gas [Member]
Disclosure Environmental Matters Details [Line Items]
Environmental Exit Costs, Reasonably Possible Additional Loss	$ 2