Employee Benefit Plans (Other Changes In Plan Assets And Projected Benefit Obligations Recognized In Accumulated Other Comprehensive Income And Regulatory Assets) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Duke Energy Corp [Member]
Regulatory Assets	$ 4,046	$ 3,390
Regulatory liabilities	3,006	3,155
Qualified Pension Plans [Member]
Regulatory assets, net increase (decrease)	152	350
Deferred income tax asset	(10)	143
Actuarial gain/loss arising during the year	60	(5)
Amortization of prior year actuarial losses	(8)	(16)
Reclassification of actuarial losses to regulatory assets	8	(365)
Amortization of prior year prior service cost	(1)	(3)
Reclassification of prior service cost to regulatory assets		(19)
Net amount recognized in accumulated other comprehensive (income)/loss	49	(265)
Qualified Pension Plans [Member] | Plan Assets And Projected Benefit Obligation [Member]
Other accumulated comprehensive income actuarial gains, recognized	2	3
Non-Qualified Pension Plans [Member]
Regulatory assets, net increase (decrease)	2	23
Regulatory liabilities	7	3
Deferred income tax asset	(1)	8
Actuarial gain/loss arising during the year	1	(8)
Reclassification of actuarial losses to regulatory assets		(1)
Amortization of prior year prior service cost		(2)
Reclassification of prior service cost to regulatory assets		(1)
Reclassification of prior service cost to regulatory liabilities		(8)
Net amount recognized in accumulated other comprehensive (income)/loss		(12)
Other Post-Retirement Benefit Plans [Member] | Plan Assets And Projected Benefit Obligation [Member]
Regulatory assets, net increase (decrease)	(22)	(14)
Regulatory liabilities	21	(5)
Deferred income tax liability	1	1
Actuarial gain/loss arising during the year		(3)
Amortization of prior year actuarial losses	1	1
Reclassification of actuarial losses to regulatory liabilities		(8)
Amortization of prior year prior service cost		2
Reclassification of prior service cost to regulatory liabilities		9
Amortization of prior year net transition liability		2
Reclassification of net transition liability to regulatory liabilities		(2)
Net amount recognized in accumulated other comprehensive (income)/loss	$ 2	$ (2)