Investments In Unconsolidated Affiliates (Summarized Combined Financial Information Of Equity Method Unconsolidated Affiliates - Income Statement) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Investments In Unconsolidated Affiliates And Related Party Transactions [Line Items]
Operating revenues	$ 5,695	$ 6,722	$ 3,577	$ 3,630	$ 3,368	$ 3,964	$ 3,534	$ 3,663	$ 19,624	$ 14,529	$ 14,272
Net Income Attributable to Duke Energy Corporation	435	594	444	295	288	472	435	511	1,768	1,706	1,320
Equity Method Investments [Member]
Investments In Unconsolidated Affiliates And Related Party Transactions [Line Items]
Operating revenues									1,624	1,615	1,385
Operating Expense									727	865	924
Net Income Attributable to Duke Energy Corporation									$ 665	$ 607	$ 430