Investments In Debt And Equity Securities (Maturities) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013
Debt Instrument [Line Items]
1 year	$ 328
1 through 5 years	435
6 to 10 years	398
Thereafter	788
Total	1,949
Duke Energy Carolinas [Member]
Debt Instrument [Line Items]
1 year	18
1 through 5 years	173
6 to 10 years	185
Thereafter	365
Total	741
Progress Energy [Member]
Debt Instrument [Line Items]
1 year	26
1 through 5 years	145
6 to 10 years	164
Thereafter	315
Total	650
Duke Energy Progress [Member]
Debt Instrument [Line Items]
1 year	11
1 through 5 years	128
6 to 10 years	76
Thereafter	208
Total	423
Duke Energy Florida [Member]
Debt Instrument [Line Items]
1 year	15
1 through 5 years	17
6 to 10 years	88
Thereafter	107
Total	227
Duke Energy Indiana [Member]
Debt Instrument [Line Items]
1 year	1
1 through 5 years	21
6 to 10 years	4
Thereafter	3
Total	$ 29