Variable Interest Entities (Consolidated VIEs) (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011	Sep. 30, 2011	Dec. 31, 2010
Cash and cash equivalents	$ 1,761	$ 2,110	$ 2,032	$ 1,670
Restricted Receivables of VIEs	1,250	1,157
Other Current Assets	2,123	1,051
Intangibles, net	359	363
Restricted Other Assets of VIEs	115	135
Other Assets	2,186	2,231
Property, Plant and Equipment Cost, VIEs	961	913
Less: Accumulated depreciation and amortization	(32,318)	(18,709)
Other Deferred Debits	163	153
Accounts payable	1,912	1,433
Non-Recourse Notes Payable	275	273
Current Maturities of Long-Term Debt	2,488	1,894
Other Current Liabilities	2,206	1,091
Non-Recourse Long-Term Debt	911	949
Deferred income taxes	10,317	7,581
Asset Retirement Obligation	4,846	1,936
Other Liabilities	2,349	1,778
Noncontrolling interests	90	93
Duke Energy Carolinas [Member]
Cash and cash equivalents	314	289	318	153
Restricted Receivables of VIEs	738	581
Other Current Assets	445	278
Other Assets	804	968
Less: Accumulated depreciation and amortization	(11,553)	(11,269)
Other Deferred Debits	72	71
Accounts payable	426	637
Current Maturities of Long-Term Debt	427	1,178
Other Current Liabilities	519	398
Non-Recourse Long-Term Debt	300	300
Deferred income taxes	5,063	4,555
Asset Retirement Obligation	1,934	1,846
Other Liabilities	955	926
Duke Energy Corp [Member]
Current Maturities of Long-Term Debt	250
Variable Interest Entity [Member]
Cash and cash equivalents	0
Variable Interest Entity [Member] | DERF [Member]
Cash and cash equivalents	0
Variable Interest Entity [Member] | Cinergy Receivables [Member]
Restricted Receivables of VIEs	486	547
Total Assets	486	547
Non-Recourse Notes Payable	275	273
Total Liabilities	275	273
Net Assets of Consolidated VIEs	211	274
Variable Interest Entity [Member] | CinCap V [Member]
Restricted Receivables of VIEs	15	13
Other Current Assets	2	2
Restricted Other Assets of VIEs	55	65
Other Assets	11	14
Total Assets	83	94
Current Maturities of Long-Term Debt	12	11
Other Current Liabilities	3	3
Non-Recourse Long-Term Debt	51	60
Other Liabilities	10	13
Total Liabilities	76	87
Net Assets of Consolidated VIEs	7	7
Variable Interest Entity [Member] | Renewables [Member]
Restricted Receivables of VIEs	8	13
Other Current Assets	143	124
Intangibles, net	12	12
Restricted Other Assets of VIEs	3	10
Other Assets	0	36
Property, Plant and Equipment Cost, VIEs	945	913
Less: Accumulated depreciation and amortization	(89)	(62)
Other Deferred Debits	23	24
Total Assets	1,045	1,070
Accounts payable	1	1
Taxes accrued	5	3
Current Maturities of Long-Term Debt	31	49
Other Current Liabilities	20	59
Non-Recourse Long-Term Debt	502	528
Deferred income taxes	158	160
Asset Retirement Obligation	14	13
Other Liabilities	45	37
Total Liabilities	776	850
Net Assets of Consolidated VIEs	269	220
Variable Interest Entity [Member] | Other VIEs [Member]
Cash and cash equivalents	0
Restricted Receivables of VIEs	3	3
Other Current Assets	11	8
Restricted Other Assets of VIEs	57	60
Other Assets	1
Property, Plant and Equipment Cost, VIEs	16
Less: Accumulated depreciation and amortization	(5)
Other Deferred Debits	1	2
Total Assets	84	73
Accounts payable	2	1
Current Maturities of Long-Term Debt	5	5
Other Current Liabilities	(1)
Non-Recourse Long-Term Debt	58	61
Other Liabilities	(1)
Total Liabilities	63	67
Noncontrolling interests	2	1
Net Assets of Consolidated VIEs	19	5
Variable Interest Entity [Member] | Total Consolidated VIE {Member]
Restricted Receivables of VIEs	1,250	1,157
Other Current Assets	156	134
Intangibles, net	12	12
Restricted Other Assets of VIEs	115	135
Other Assets	12	50
Property, Plant and Equipment Cost, VIEs	961	913
Less: Accumulated depreciation and amortization	(94)	(62)
Other Deferred Debits	24	26
Total Assets	2,436	2,365
Accounts payable	3	2
Non-Recourse Notes Payable	275	273
Taxes accrued	5	3
Current Maturities of Long-Term Debt	48	65
Other Current Liabilities	22	62
Non-Recourse Long-Term Debt	911	949
Deferred income taxes	158	160
Asset Retirement Obligation	14	13
Other Liabilities	54	50
Total Liabilities	1,490	1,577
Noncontrolling interests	2	1
Net Assets of Consolidated VIEs	944	787
Variable Interest Entity [Member] | Duke Energy Carolinas [Member] | DERF [Member]
Restricted Receivables of VIEs	738	581
Total Assets	738	581
Non-Recourse Long-Term Debt	300	300
Total Liabilities	300	300
Net Assets of Consolidated VIEs	$ 438	$ 281