Investments in Debt and Equity Securities (Maturities) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013
Debt Instrument [Line Items]
1 year	$ 89
1 through 5 years	431
6 to 10 years	426
Thereafter	804
Total	1,750
Duke Energy Carolinas [Member]
Debt Instrument [Line Items]
1 year	18
1 through 5 years	167
6 to 10 years	239
Thereafter	407
Total	831
Progress Energy [Member]
Debt Instrument [Line Items]
1 year	12
1 through 5 years	206
6 to 10 years	131
Thereafter	306
Total	655
Duke Energy Progress [Member]
Debt Instrument [Line Items]
1 year	7
1 through 5 years	122
6 to 10 years	89
Thereafter	203
Total	421
Duke Energy Florida [Member]
Debt Instrument [Line Items]
1 year	5
1 through 5 years	84
6 to 10 years	42
Thereafter	103
Total	234
Duke Energy Indiana [Member]
Debt Instrument [Line Items]
1 year	1
1 through 5 years	21
6 to 10 years	4
Thereafter	2
Total	$ 28