Fair Value Of Financial Assets And Liabilities (Fair Value Measurement Amounts For Assets And Liabilities) (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Investments in available-for-sale auction rate securities, fair value	$ 41	$ 71
Nuclear decommissioning trust fund equity securities	2,779	1,337
Nuclear decommissioning trust fund debt securities	1,376	723
Other long-term trading and available-for-sale equity securities	77	68
Other trading and available-for sale debt securities	650	382
Derivative assets	89	74
Assets, Fair Value Disclosure, Total	5,012	2,655
Derivative liabilities	(776)	(264)
Net Assets Fair Value, Total	4,236	2,391
Duke Energy Carolinas [Member]
Investments in available-for-sale auction rate securities, fair value	6	12
Nuclear decommissioning trust fund equity securities	1,553	1,337
Nuclear decommissioning trust fund debt securities	758	723
Derivative assets		1
Assets, Fair Value Disclosure, Total	2,317	2,073
Derivative liabilities	(12)
Net Assets Fair Value, Total	2,305
Duke Energy Ohio [Member]
Derivative assets	40	56
Assets, Fair Value Disclosure, Total	40	56
Derivative liabilities	(46)	(30)
Net Assets Fair Value, Total	(6)	26
Duke Energy Indiana [Member]
Available-for-sale Securities, Equity Securities	49	46
Available-for-sale Securities, Debt Securities	28	28
Derivative assets	17	4
Assets, Fair Value Disclosure, Total	94	78
Derivative liabilities	(71)	(69)
Net Assets Fair Value, Total	23	9
Level 1 [Member]
Nuclear decommissioning trust fund equity securities	2,707	1,285
Nuclear decommissioning trust fund debt securities	234	109
Other long-term trading and available-for-sale equity securities	68	61
Other trading and available-for sale debt securities	66	22
Derivative assets	0	43
Assets, Fair Value Disclosure, Total	3,075	1,520
Derivative liabilities	(24)	(36)
Net Assets Fair Value, Total	3,051	1,484
Level 1 [Member] | Duke Energy Carolinas [Member]
Nuclear decommissioning trust fund equity securities	1,487	1,285
Nuclear decommissioning trust fund debt securities	102	109
Assets, Fair Value Disclosure, Total	1,589	1,394
Net Assets Fair Value, Total	1,589
Level 1 [Member] | Duke Energy Ohio [Member]
Derivative assets	27	42
Assets, Fair Value Disclosure, Total	27	42
Derivative liabilities	(20)	(10)
Net Assets Fair Value, Total	7	32
Level 1 [Member] | Duke Energy Indiana [Member]
Available-for-sale Securities, Equity Securities	49	46
Derivative assets	0
Assets, Fair Value Disclosure, Total	49	46
Derivative liabilities		(1)
Net Assets Fair Value, Total	49	45
Level 2 [Member]
Nuclear decommissioning trust fund equity securities	53	46
Nuclear decommissioning trust fund debt securities	1,095	567
Other long-term trading and available-for-sale equity securities	9	7
Other trading and available-for sale debt securities	584	360
Derivative assets	10	6
Assets, Fair Value Disclosure, Total	1,751	986
Derivative liabilities	(598)	(164)
Net Assets Fair Value, Total	1,153	822
Level 2 [Member] | Duke Energy Carolinas [Member]
Nuclear decommissioning trust fund equity securities	47	46
Nuclear decommissioning trust fund debt securities	609	567
Derivative assets		1
Assets, Fair Value Disclosure, Total	656	614
Net Assets Fair Value, Total	656
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	28	28
Derivative assets	0
Assets, Fair Value Disclosure, Total	28	28
Derivative liabilities	(71)	(68)
Net Assets Fair Value, Total	(43)	(40)
Level 3 [Member]
Investments in available-for-sale auction rate securities, fair value	41	71
Nuclear decommissioning trust fund equity securities	19	6
Nuclear decommissioning trust fund debt securities	47	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	79	25
Assets, Fair Value Disclosure, Total	186	149
Derivative liabilities	(154)	(64)
Net Assets Fair Value, Total	32	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		6
Nuclear decommissioning trust fund debt securities	47	47
Assets, Fair Value Disclosure, Total	72	65
Derivative liabilities	(12)
Net Assets Fair Value, Total	60
Level 3 [Member] | Duke Energy Ohio [Member]
Derivative assets	9	9
Assets, Fair Value Disclosure, Total	9	9
Derivative liabilities	(17)	(12)
Net Assets Fair Value, Total	(8)	(3)
Level 3 [Member] | Duke Energy Indiana [Member]
Derivative assets	17	4
Assets, Fair Value Disclosure, Total	17	4
Net Assets Fair Value, Total	$ 17	$ 4