Investments in Debt and Equity Securities (Unrealized Losses Of Available-For-Sale Debt and Equity Securities in A Continuous Loss Position) (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013 Equity Securities [Member] Ndtf [Member]	Dec. 31, 2012 Equity Securities [Member] Ndtf [Member]	Jun. 30, 2013 Equity Securities [Member] Other Classification [Member]		Dec. 31, 2012 Equity Securities [Member] Other Classification [Member]		Jun. 30, 2013 Auction Rate Securities [Member]		Dec. 31, 2012 Auction Rate Securities [Member]		Jun. 30, 2013 Duke Energy Carolinas [Member] Equity Securities [Member] Ndtf [Member]	Dec. 31, 2012 Duke Energy Carolinas [Member] Equity Securities [Member] Ndtf [Member]	Jun. 30, 2013 Duke Energy Carolinas [Member] Auction Rate Securities [Member]		Dec. 31, 2012 Duke Energy Carolinas [Member] Auction Rate Securities [Member]		Jun. 30, 2013 Progress Energy [Member] Equity Securities [Member] Ndtf [Member]	Dec. 31, 2012 Progress Energy [Member] Equity Securities [Member] Ndtf [Member]	Jun. 30, 2013 Duke Energy Progress [Member] Equity Securities [Member] Ndtf [Member]	Dec. 31, 2012 Duke Energy Progress [Member] Equity Securities [Member] Ndtf [Member]	Jun. 30, 2013 Duke Energy Florida [Member] Equity Securities [Member] Ndtf [Member]	Jun. 30, 2012 Duke Energy Florida [Member] Equity Securities [Member] Ndtf [Member]	Jun. 30, 2013 Duke Energy Indiana [Member] Equity Securities [Member] Other Classification [Member]		Dec. 31, 2012 Duke Energy Indiana [Member] Equity Securities [Member] Other Classification [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair value of investments	$ 3,170	$ 2,837	$ 88	[1]	$ 72	[1]	$ 26	[2]	$ 29	[2]	$ 1,763	$ 1,592	$ 3	[3]	$ 3	[3]	$ 1,407	$ 1,245	$ 918	$ 811	$ 489	$ 435	$ 56	[2]	$ 49	[2]

[1] Included in Other within Current Assets and Other within Investments and Other Assets on the Condensed Consolidated Balance Sheet.

[2] Included in Other within Investments and Other Assets on the Condensed Consolidated Balance Sheets.

[3] Included in Other within Investments and Other Assets on the Condensed Consolidated Balance Sheets.