Fair Value Of Financial Assets And Liabilities (Fair Value Measurement Amounts For Assets And Liabilities) (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Investments in available-for-sale auction rate securities, fair value	$ 41	$ 71
Nuclear decommissioning trust fund equity securities	1,470	1,337
Nuclear decommissioning trust fund debt securities	734	723
Other long-term trading and available-for-sale equity securities	74	68
Other trading and available-for sale debt securities	481	382
Derivative assets	89	74
Assets, Fair Value Disclosure, Total	2,889	2,655
Derivative liabilities	(298)	(264)
Net Assets Fair Value, Total	2,591	2,391
Duke Energy Carolinas [Member]
Investments in available-for-sale auction rate securities, fair value	6	12
Nuclear decommissioning trust fund equity securities	1,470	1,337
Nuclear decommissioning trust fund debt securities	734	723
Derivative assets	1	1
Assets, Fair Value Disclosure, Total	2,211	2,073
Duke Energy Ohio [Member]
Derivative assets	74	56
Assets, Fair Value Disclosure, Total	74	56
Derivative liabilities	(30)	(30)
Net Assets Fair Value, Total	44	26
Duke Energy Indiana [Member]
Available-for-sale Securities, Equity Securities	46	46
Available-for-sale Securities, Debt Securities	29	28
Derivative assets	23	4
Assets, Fair Value Disclosure, Total	98	78
Derivative liabilities	(76)	(69)
Net Assets Fair Value, Total	22	9
Level 1 [Member]
Nuclear decommissioning trust fund equity securities	1,406	1,285
Nuclear decommissioning trust fund debt securities	78	109
Other long-term trading and available-for-sale equity securities	66	61
Other trading and available-for sale debt securities	28	22
Derivative assets	16	43
Assets, Fair Value Disclosure, Total	1,594	1,520
Derivative liabilities	(12)	(36)
Net Assets Fair Value, Total	1,582	1,484
Level 1 [Member] | Duke Energy Carolinas [Member]
Nuclear decommissioning trust fund equity securities	1,406	1,285
Nuclear decommissioning trust fund debt securities	78	109
Assets, Fair Value Disclosure, Total	1,484	1,394
Level 1 [Member] | Duke Energy Ohio [Member]
Derivative assets	62	42
Assets, Fair Value Disclosure, Total	62	42
Derivative liabilities	(11)	(10)
Net Assets Fair Value, Total	51	32
Level 1 [Member] | Duke Energy Indiana [Member]
Available-for-sale Securities, Equity Securities	46	46
Derivative assets	1
Assets, Fair Value Disclosure, Total	47	46
Derivative liabilities		(1)
Net Assets Fair Value, Total	47	45
Level 2 [Member]
Nuclear decommissioning trust fund equity securities	46	46
Nuclear decommissioning trust fund debt securities	610	567
Other long-term trading and available-for-sale equity securities	8	7
Other trading and available-for sale debt securities	453	360
Derivative assets	9	6
Assets, Fair Value Disclosure, Total	1,126	986
Derivative liabilities	(203)	(164)
Net Assets Fair Value, Total	923	822
Level 2 [Member] | Duke Energy Carolinas [Member]
Nuclear decommissioning trust fund equity securities	46	46
Nuclear decommissioning trust fund debt securities	610	567
Derivative assets	1	1
Assets, Fair Value Disclosure, Total	657	614
Level 2 [Member] | Duke Energy Ohio [Member]
Derivative assets	4	5
Assets, Fair Value Disclosure, Total	4	5
Derivative liabilities	(9)	(8)
Net Assets Fair Value, Total	(5)	(3)
Level 2 [Member] | Duke Energy Indiana [Member]
Available-for-sale Securities, Debt Securities	29	28
Derivative assets	0
Assets, Fair Value Disclosure, Total	29	28
Derivative liabilities	(76)	(68)
Net Assets Fair Value, Total	(47)	(40)
Level 3 [Member]
Investments in available-for-sale auction rate securities, fair value	41	71
Nuclear decommissioning trust fund equity securities	18	6
Nuclear decommissioning trust fund debt securities	46	47
Other long-term trading and available-for-sale equity securities	0	0
Other trading and available-for sale debt securities	0	0
Derivative assets	64	25
Assets, Fair Value Disclosure, Total	169	149
Derivative liabilities	(83)	(64)
Net Assets Fair Value, Total	86	85
Level 3 [Member] | Duke Energy Carolinas [Member]
Investments in available-for-sale auction rate securities, fair value	6	12
Nuclear decommissioning trust fund equity securities	18	6
Nuclear decommissioning trust fund debt securities	46	47
Assets, Fair Value Disclosure, Total	70	65
Level 3 [Member] | Duke Energy Ohio [Member]
Derivative assets	8	9
Assets, Fair Value Disclosure, Total	8	9
Derivative liabilities	(10)	(12)
Net Assets Fair Value, Total	(2)	(3)
Level 3 [Member] | Duke Energy Indiana [Member]
Derivative assets	22	4
Assets, Fair Value Disclosure, Total	22	4
Net Assets Fair Value, Total	$ 22	$ 4