Investments In Unconsolidated Affiliates And Related Party Transactions (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, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Revenues									$ 14,529	$ 14,272	$ 12,731
Net Income Attributable to Duke Energy Corporation	288	472	435	511	427	670	(222)	445	1,706	1,320	1,075
Equity Method Investments [Member]
Revenues									1,615	1,385	1,509
Operating Expenses									865	924	1,252
Net Income Attributable to Duke Energy Corporation									$ 607	$ 430	$ 257