Employee Benefit Plans (Narrative) (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended	12 Months Ended
	Sep. 30, 2014	Dec. 31, 2014	Dec. 31, 2013
Defined Benefit Plan Disclosure [Line Items]
Maximum years of participation	35 years	35 years
Master Trust [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of securities on loan		383	$ 43
Qualified Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Average remaining service period, in years		9 years
Qualified Pension Plans [Member] | Master Trust [Member]
Defined Benefit Plan Disclosure [Line Items]
Master trust allocation percentage		98.00%
Non-Qualified Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Average remaining service period, in years		13 years
Other Post-Retirement Benefit Plans [Member] | Master Trust [Member]
Defined Benefit Plan Disclosure [Line Items]
Master trust allocation percentage		2.00%
Duke Energy Carolinas [Member] | Qualified Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Average remaining service period, in years		9 years
Duke Energy Carolinas [Member] | Non-Qualified Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Average remaining service period, in years		9 years
Progress Energy [Member] | Qualified Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Average remaining service period, in years		9 years
Progress Energy [Member] | Non-Qualified Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Average remaining service period, in years		13 years
Duke Energy Progress [Member] | Qualified Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Average remaining service period, in years		9 years
Duke Energy Progress [Member] | Non-Qualified Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Average remaining service period, in years		12 years
Duke Energy Florida [Member] | Qualified Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Average remaining service period, in years		9 years
Duke Energy Florida [Member] | Non-Qualified Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Average remaining service period, in years		17 years
Duke Energy Ohio [Member] | Qualified Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Average remaining service period, in years		9 years
Duke Energy Ohio [Member] | Non-Qualified Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Average remaining service period, in years		9 years
Duke Energy Indiana [Member] | Qualified Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Average remaining service period, in years		9 years
Duke Energy Indiana [Member] | Non-Qualified Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Average remaining service period, in years		9 years