Goodwill (Schedule of Intangible Assets) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	$ 595	$ 570
Accumulated amortization	(223)	(207)
Total intangible assets, net	372	363
Duke Energy Ohio [Member]
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	306	310
Accumulated amortization	(177)	(167)
Total intangible assets, net	129	143
Duke Energy Indiana [Member]
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	53	61
Accumulated amortization	(12)	(11)
Total intangible assets, net	41	50
Emission Allowances [Member]
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	80	66	175
Emission Allowances [Member] | Duke Energy Ohio [Member]
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	24	29	125
Emission Allowances [Member] | Duke Energy Indiana [Member]
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	29	37	49
Gas Coal And Power Contracts [Member]
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	295	295
Accumulated amortization	(180)	(169)
Gas Coal And Power Contracts [Member] | Duke Energy Ohio [Member]
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	272	271
Accumulated amortization	(168)	(158)
Gas Coal And Power Contracts [Member] | Duke Energy Indiana [Member]
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	24	24
Accumulated amortization	(12)	(11)
Wind Development Rights [Member]
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	111	137
Accumulated amortization	(9)	(7)
OtherIntangibleAssets
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	109	72
Accumulated amortization	(34)	(31)
OtherIntangibleAssets | Duke Energy Ohio [Member]
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	10	10
Accumulated amortization	$ (9)	$ (9)