Variable Interest Entities (Non-Consolidated VIEs) (Details) (USD $) In Millions	Sep. 30, 2011	Dec. 31, 2010	Sep. 30, 2010	Dec. 31, 2009
Investments in equity method unconsolidated affiliates	$ 459	$ 444
Intangibles	371	467
Other Current Liabilities	1,046	1,170
Deferred Credits and Other Liabilities	15,178	14,605
Total common stockholder's equity	22,794	22,522
Consolidated VIEs [Member]
Intangibles	12	13
Other Current Liabilities	62	21
Total common stockholder's equity	738	1,170
Consolidated VIEs [Member] | Renewables [Member]
Intangibles	12	13
Other Current Liabilities	57	16
Total common stockholder's equity	169	414
Consolidated VIEs [Member] | Other VIEs [Member]
Total common stockholder's equity	8	(2)
Duke Energy Ohio [Member] | Non-Consolidated VIEs [Member]
Receivables	87	216
Intangibles	113	119
Total Assets	200	335
Total common stockholder's equity	200	335
Duke Energy Indiana [Member] | Non-Consolidated VIEs [Member]
Receivables	122	192
Total Assets	122	192
Total common stockholder's equity	122	192
DukeNet [Member] | Non-Consolidated VIEs [Member]
Investments in equity method unconsolidated affiliates	130	137
Total Assets	130	137
Total common stockholder's equity	130	137
Non-Consolidated VIEs [Member]
Investments in equity method unconsolidated affiliates	239	255
Intangibles	113	119
Total Assets	352	374
Other Current Liabilities	1	3
Deferred Credits and Other Liabilities	18	28
Total Liabilities	19	31
Total common stockholder's equity	333	343
Non-Consolidated VIEs [Member] | Renewables [Member]
Investments in equity method unconsolidated affiliates	84	95
Total Assets	84	95
Total common stockholder's equity	84	95
Non-Consolidated VIEs [Member] | Other VIEs [Member]
Investments in equity method unconsolidated affiliates	25	23
Intangibles	113	119
Total Assets	138	142
Other Current Liabilities	1	3
Deferred Credits and Other Liabilities	18	28
Total Liabilities	19	31
Total common stockholder's equity	119	111
Duke Energy Ohio [Member]
Intangibles	148	248
Other Current Liabilities	92	99
Deferred Credits and Other Liabilities	2,390	2,255
Total common stockholder's equity	5,136	5,464	5,445	5,898
Duke Energy Indiana [Member]
Intangibles	53	64
Other Current Liabilities	90	99
Deferred Credits and Other Liabilities	2,063	2,087
Total common stockholder's equity	$ 3,679	$ 3,567	$ 3,501	$ 2,934