Investments in Debt and Equity Securities (Maturities) (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2014
Debt Instrument [Line Items]
Due in one year or less	$ 57
Due after one through five years	459
Due after five through 10 years	440
Due after 10 years	793
Total	1,749
Duke Energy Carolinas [Member]
Debt Instrument [Line Items]
Due in one year or less	24
Due after one through five years	182
Due after five through 10 years	243
Due after 10 years	364
Total	813
Progress Energy [Member]
Debt Instrument [Line Items]
Due in one year or less	24
Due after one through five years	217
Due after five through 10 years	141
Due after 10 years	327
Total	709
Duke Energy Progress [Member]
Debt Instrument [Line Items]
Due in one year or less	15
Due after one through five years	141
Due after five through 10 years	90
Due after 10 years	220
Total	466
Duke Energy Florida [Member]
Debt Instrument [Line Items]
Due in one year or less	9
Due after one through five years	76
Due after five through 10 years	51
Due after 10 years	107
Total	243
Duke Energy Indiana [Member]
Debt Instrument [Line Items]
Due in one year or less	1
Due after one through five years	19
Due after five through 10 years	7
Due after 10 years	3
Total	$ 30