Condensed Consolidated Statements Of Cash Flows (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	$ 299	$ 513
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation and amortization (including amortization of nuclear fuel)	544	504
Equity component of AFUDC	(59)	(60)
Gains on sales of other assets	(3)	(13)
Impairment of other long-lived assets	407
Deferred income taxes	65	175
Voluntary opportunity cost deferral	(101)
Equity in earnings of unconsolidated affiliates	(45)	(32)
Accrued pension and other post-retirement benefit costs	28	26
(Increase) decrease in
Net realized and unrealized mark-to-market and hedging transactions	(2)	18
Receivables	172	218
Inventory	(162)	(31)
Other current assets	110	96
Increase (decrease) in
Accounts payable	(270)	(192)
Taxes accrued	(62)	(29)
Other current liabilities	10	(193)
Other assets	3	27
Other liabilities	(62)	(66)
Net cash provided by operating activities	872	961
CASH FLOWS FROM INVESTING ACTIVITIES
Capital expenditures	(988)	(1,006)
Investment expenditures	(13)	(3)
Acquisitions	(42)	(2)
Purchases of available-for-sale securities	(948)	(710)
Proceeds from sales and maturities of available-for-sale securities	821	675
Net proceeds from the sales of other assets, and sales of and collections on notes receivable	17	103
Change in restricted cash	(35)	14
Other	8	11
Net cash used in investing activities	(1,180)	(918)
CASH FLOWS FROM FINANCING ACTIVITIES
Proceeds from the issuance of long-term debt	392
Proceeds from the issuance of common stock related to employee benefit plans	8	6
Payments for the redemption of long-term debt	(821)	(18)
Notes payable and commercial paper	28	58
Distributions to noncontrolling interests	(1)	(10)
Dividends paid	(335)	(331)
Other	(2)	1
Net cash used in financing activities	(731)	(294)
Net increase in cash and cash equivalents	(1,039)	(251)
Cash and cash equivalents at beginning of period	2,110	1,670
Cash and cash equivalents at end of period	1,071	1,419
Supplemental Disclosures
Accrued capital expenditures	270	282
Extinguishment of debt related to investment in Attiki Gas Supply, S.A.	66
Duke Energy Carolinas [Member]
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	266	205
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation and amortization (including amortization of nuclear fuel)	288	249
Equity component of AFUDC	(36)	(39)
Gains on sales of other assets	(3)
Deferred income taxes	154	119
Voluntary opportunity cost deferral	(101)
Accrued pension and other post-retirement benefit costs	10	8
(Increase) decrease in
Receivables	117	246
Inventory	(100)	(59)
Other current assets	(3)	147
Increase (decrease) in
Accounts payable	(233)	(116)
Taxes accrued	(65)	(56)
Other current liabilities	109	(40)
Other assets	(18)	(4)
Other liabilities	(32)	(43)
Net cash provided by operating activities	353	617
CASH FLOWS FROM INVESTING ACTIVITIES
Capital expenditures	(483)	(562)
Purchases of available-for-sale securities	(627)	(428)
Proceeds from sales and maturities of available-for-sale securities	615	416
Notes due from affiliate	625	(104)
Other	(5)
Net cash used in investing activities	125	(678)
CASH FLOWS FROM FINANCING ACTIVITIES
Payments for the redemption of long-term debt	(751)	(1)
Other	(1)
Net cash used in financing activities	(752)	(1)
Net increase in cash and cash equivalents	(274)	(62)
Cash and cash equivalents at beginning of period	289	153
Cash and cash equivalents at end of period	15	91
Supplemental Disclosures
Accrued capital expenditures	115	153
Duke Energy Ohio [Member]
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	74	73
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation and amortization (including amortization of nuclear fuel)	84	89
Gains on sales of other assets	(1)	(2)
Impairment of other long-lived assets	2
Deferred income taxes	44	36
Accrued pension and other post-retirement benefit costs	3	4
(Increase) decrease in
Net realized and unrealized mark-to-market and hedging transactions	(48)	(2)
Receivables	55	78
Inventory	(8)	33
Other current assets	42	14
Increase (decrease) in
Accounts payable	16	(64)
Taxes accrued	(24)	10
Other current liabilities	6	(1)
Other assets	(8)	4
Other liabilities	(57)	(28)
Net cash provided by operating activities	180	244
CASH FLOWS FROM INVESTING ACTIVITIES
Capital expenditures	(121)	(96)
Net proceeds from the sales of other assets, and sales of and collections on notes receivable	82
Notes due from affiliate	(218)	(4)
Change in restricted cash	6	4
Other		6
Net cash used in investing activities	(251)	(90)
CASH FLOWS FROM FINANCING ACTIVITIES
Payments for the redemption of long-term debt	(2)	(2)
Notes payable to affiliate		3
Dividend to parent		(285)
Net cash used in financing activities	(2)	(284)
Net increase in cash and cash equivalents	(73)	(130)
Cash and cash equivalents at beginning of period	99	228
Cash and cash equivalents at end of period	26	98
Supplemental Disclosures
Accrued capital expenditures	34	35
Transfer of Vermillion Generating Station	28
Duke Energy Indiana [Member]
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	(167)	76
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation and amortization (including amortization of nuclear fuel)	97	100
Equity component of AFUDC	(21)	(19)
Impairment of other long-lived assets	400
Deferred income taxes	(116)	7
Accrued pension and other post-retirement benefit costs	4	5
(Increase) decrease in
Receivables	(11)	77
Inventory	(34)	(12)
Other current assets	8	20
Increase (decrease) in
Accounts payable	15	12
Taxes accrued	(8)	26
Other current liabilities	(4)	(17)
Other assets	9	3
Other liabilities	(19)	(12)
Net cash provided by operating activities	153	266
CASH FLOWS FROM INVESTING ACTIVITIES
Capital expenditures	(273)	(269)
Purchases of available-for-sale securities	(4)	(1)
Proceeds from sales and maturities of available-for-sale securities	4
Notes due from affiliate		(2)
Change in restricted cash		5
Other	1
Net cash used in investing activities	(272)	(267)
CASH FLOWS FROM FINANCING ACTIVITIES
Proceeds from the issuance of long-term debt	250
Payments for the redemption of long-term debt	(1)	(1)
Notes payable to affiliate	(122)
Other	(2)
Net cash used in financing activities	125	(1)
Net increase in cash and cash equivalents	6	(2)
Cash and cash equivalents at beginning of period	16	54
Cash and cash equivalents at end of period	22	52
Supplemental Disclosures
Accrued capital expenditures	72	86
Transfer of Vermillion Generating Station	$ 26