Employee Benefit Plans (Information For Plans with Accumulated Benefit Obligation in Excess of Plan Assets) (Details) - Pension Plan [Member] - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Qualified Plan [Member]
Information For Plans With Accumulated Benefit Obligation In Excess Of Plan Assets [Abstract]
Projected benefit obligation	$ 1,386	$ 1,299
Accumulated benefit obligation	1,326	1,239
Fair value of plan assets	1,260	1,182
Nonqualified Plan [Member]
Information For Plans With Accumulated Benefit Obligation In Excess Of Plan Assets [Abstract]
Projected benefit obligation	331	332
Accumulated benefit obligation	331	332
Duke Energy Carolinas [Member] | Nonqualified Plan [Member]
Information For Plans With Accumulated Benefit Obligation In Excess Of Plan Assets [Abstract]
Projected benefit obligation	14	14
Accumulated benefit obligation	14	14
Progress Energy [Member] | Qualified Plan [Member]
Information For Plans With Accumulated Benefit Obligation In Excess Of Plan Assets [Abstract]
Projected benefit obligation	718	665
Accumulated benefit obligation	683	633
Fair value of plan assets	650	604
Progress Energy [Member] | Nonqualified Plan [Member]
Information For Plans With Accumulated Benefit Obligation In Excess Of Plan Assets [Abstract]
Projected benefit obligation	116	114
Accumulated benefit obligation	116	114
Duke Energy Progress [Member] | Nonqualified Plan [Member]
Information For Plans With Accumulated Benefit Obligation In Excess Of Plan Assets [Abstract]
Projected benefit obligation	35	33
Accumulated benefit obligation	35	33
Duke Energy Florida [Member] | Qualified Plan [Member]
Information For Plans With Accumulated Benefit Obligation In Excess Of Plan Assets [Abstract]
Projected benefit obligation	718	665
Accumulated benefit obligation	683	633
Fair value of plan assets	650	604
Duke Energy Florida [Member] | Nonqualified Plan [Member]
Information For Plans With Accumulated Benefit Obligation In Excess Of Plan Assets [Abstract]
Projected benefit obligation	47	46
Accumulated benefit obligation	47	46
Duke Energy Ohio [Member] | Qualified Plan [Member]
Information For Plans With Accumulated Benefit Obligation In Excess Of Plan Assets [Abstract]
Projected benefit obligation	337	311
Accumulated benefit obligation	326	299
Fair value of plan assets	308	286
Duke Energy Ohio [Member] | Nonqualified Plan [Member]
Information For Plans With Accumulated Benefit Obligation In Excess Of Plan Assets [Abstract]
Projected benefit obligation	4	4
Accumulated benefit obligation	4	4
Duke Energy Indiana [Member] | Nonqualified Plan [Member]
Information For Plans With Accumulated Benefit Obligation In Excess Of Plan Assets [Abstract]
Projected benefit obligation	3	3
Accumulated benefit obligation	3	3
Piedmont Natural Gas [Member] | Nonqualified Plan [Member]
Information For Plans With Accumulated Benefit Obligation In Excess Of Plan Assets [Abstract]
Projected benefit obligation	4	4
Accumulated benefit obligation	$ 4	$ 4