Variable Interest Entities (Consolidated VIEs) (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011	Jun. 30, 2011	Dec. 31, 2010
Cash and cash equivalents	$ 1,526	$ 2,110	$ 1,362	$ 1,670
Restricted Receivables of VIEs	1,233	1,157
Other Current Assets	1,122	1,051
Intangibles, net	357	363
Restricted Other Assets of VIEs	133	135
Other Assets	1,894	2,231
Property, Plant and Equipment Cost, VIEs	1,357	913
Less: Accumulated depreciation and amortization	(19,101)	(18,709)
Other Deferred Debits	159	153
Accounts payable	1,160	1,433
Non-Recourse Notes Payable	269	273
Taxes accrued	359	431
Current Maturities of Long-Term Debt	1,870	1,894
Other Current Liabilities	1,434	1,091
Non-Recourse Long-Term Debt	915	949
Deferred income taxes	7,914	7,581
Asset Retirement Obligation	1,999	1,936
Other Liabilities	1,820	1,778
Noncontrolling interests	97	93
Duke Energy Carolinas [Member]
Cash and cash equivalents	18	289	143	153
Restricted Receivables of VIEs	680	581
Other Current Assets	327	278
Other Assets	971	968
Less: Accumulated depreciation and amortization	(11,374)	(11,269)
Other Deferred Debits	68	71
Accounts payable	448	793
Taxes accrued	109	126
Current Maturities of Long-Term Debt	427	1,178
Other Current Liabilities	481	398
Non-Recourse Long-Term Debt	300	300
Deferred income taxes	4,891	4,555
Asset Retirement Obligation	1,904	1,846
Other Liabilities	900	926
Duke Energy Corp [Member]
Current Maturities of Long-Term Debt	250
Variable Interest Entity [Member] | Cinergy Receivables [Member]
Restricted Receivables of VIEs	522	547
Total Assets	522	547
Non-Recourse Notes Payable	269	273
Total Liabilities	269	273
Net Assets of Consolidated VIEs	253	274
Variable Interest Entity [Member] | CinCap V [Member]
Restricted Receivables of VIEs	14	13
Other Current Assets	2	2
Restricted Other Assets of VIEs	58	65
Other Assets	11	14
Total Assets	85	94
Current Maturities of Long-Term Debt	12	11
Other Current Liabilities	2	3
Non-Recourse Long-Term Debt	55	60
Other Liabilities	9	13
Total Liabilities	78	87
Net Assets of Consolidated VIEs	7	7
Variable Interest Entity [Member] | Renewables [Member]
Restricted Receivables of VIEs	14	13
Other Current Assets	118	124
Intangibles, net	34	12
Restricted Other Assets of VIEs	17	10
Other Assets	2	36
Property, Plant and Equipment Cost, VIEs	1,357	913
Less: Accumulated depreciation and amortization	(83)	(62)
Other Deferred Debits	34	24
Total Assets	1,493	1,070
Accounts payable	7	1
Taxes accrued	3	3
Current Maturities of Long-Term Debt	361	49
Other Current Liabilities	20	59
Non-Recourse Long-Term Debt	502	528
Deferred income taxes	155	160
Asset Retirement Obligation	18	13
Other Liabilities	42	37
Total Liabilities	1,108	850
Net Assets of Consolidated VIEs	385	220
Variable Interest Entity [Member] | Other VIEs [Member]
Restricted Receivables of VIEs	3	3
Other Current Assets	7	8
Restricted Other Assets of VIEs	58	60
Other Deferred Debits	1	2
Total Assets	69	73
Accounts payable	2	1
Current Maturities of Long-Term Debt	4	5
Other Current Liabilities	1
Non-Recourse Long-Term Debt	58	61
Total Liabilities	65	67
Noncontrolling interests	2	1
Net Assets of Consolidated VIEs	2	5
Variable Interest Entity [Member] | Total Consolidated VIE {Member]
Restricted Receivables of VIEs	1,233	1,157
Other Current Assets	127	134
Intangibles, net	34	12
Restricted Other Assets of VIEs	133	135
Other Assets	13	50
Property, Plant and Equipment Cost, VIEs	1,357	913
Less: Accumulated depreciation and amortization	(83)	(62)
Other Deferred Debits	35	26
Total Assets	2,849	2,365
Accounts payable	9	2
Non-Recourse Notes Payable	269	273
Taxes accrued	3	3
Current Maturities of Long-Term Debt	377	65
Other Current Liabilities	23	62
Non-Recourse Long-Term Debt	915	949
Deferred income taxes	155	160
Asset Retirement Obligation	18	13
Other Liabilities	51	50
Total Liabilities	1,820	1,577
Noncontrolling interests	2	1
Net Assets of Consolidated VIEs	1,027	787
Variable Interest Entity [Member] | Duke Energy Carolinas [Member] | DERF [Member]
Restricted Receivables of VIEs	680	581
Total Assets	680	581
Non-Recourse Long-Term Debt	300	300
Total Liabilities	300	300
Net Assets of Consolidated VIEs	$ 380	$ 281