Regulatory Matters (Schedule of Subsidiary Restricted Net Assets)(Details) (USD $) In Billions, unless otherwise specified	Dec. 31, 2012
Restricted net assets	$ 10.3
Duke Energy Carolinas [Member]
Restricted net assets	2.8
Progress Energy [Member]
Restricted net assets	2.0
Progress Energy Carolinas [Member]
Restricted net assets	1.9
Duke Energy Ohio [Member]
Restricted net assets	3.9	[1]
Equity Restriction	1.3
Duke Energy Indiana [Member]
Restricted net assets	$ 1.4

[1] As of December 31, 2012, the equity balance available for payment of dividends, based on the FERC and PUCO order discussed above, was $1.3 billion.