Employee Benefit Plans (Narrative) (Details) - USD ($) $ in Millions	2 Months Ended	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Oct. 31, 2016	Dec. 31, 2015	Oct. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Impact of plan conversion on next year's net periodic benefit cost		$ 33
Maximum years of participation		35 years
Master Trust [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected long-term rate of return on plan assets		6.50%
Fair value of securities on loan	$ 156	$ 195	$ 156
Pension Plan [Member] | Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Average remaining service period, in years		13 years
Expected long-term rate of return on plan assets					6.50%
Pension Plan [Member] | Nonqualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Average remaining service period, in years		11 years
Pension Plan [Member] | Master Trust [Member]
Defined Benefit Plan Disclosure [Line Items]
Master trust allocation percentage		98.00%
Other Post-Retirement Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Average remaining service period, in years		9 years
Expected long-term rate of return on plan assets		6.50%	6.50%		6.50%
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] | Pension Plan [Member] | Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Average remaining service period, in years		12 years
Duke Energy Carolinas [Member] | Pension Plan [Member] | Nonqualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Average remaining service period, in years		8 years
Duke Energy Carolinas [Member] | Other Post-Retirement Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Average remaining service period, in years		8 years
Progress Energy [Member] | Pension Plan [Member] | Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Average remaining service period, in years		12 years
Progress Energy [Member] | Pension Plan [Member] | Nonqualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Average remaining service period, in years		14 years
Progress Energy [Member] | Other Post-Retirement Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Average remaining service period, in years		6 years
Duke Energy Progress [Member] | Pension Plan [Member] | Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Average remaining service period, in years		13 years
Duke Energy Progress [Member] | Pension Plan [Member] | Nonqualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Average remaining service period, in years		11 years
Duke Energy Progress [Member] | Other Post-Retirement Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Average remaining service period, in years		6 years
Duke Energy Florida [Member] | Pension Plan [Member] | Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Average remaining service period, in years		12 years
Duke Energy Florida [Member] | Pension Plan [Member] | Nonqualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Average remaining service period, in years		15 years
Duke Energy Florida [Member] | Other Post-Retirement Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Average remaining service period, in years		7 years
Duke Energy Ohio [Member] | Pension Plan [Member] | Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Average remaining service period, in years		14 years
Duke Energy Ohio [Member] | Pension Plan [Member] | Nonqualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Average remaining service period, in years		8 years
Duke Energy Ohio [Member] | Other Post-Retirement Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Average remaining service period, in years		7 years
Duke Energy Indiana [Member] | Pension Plan [Member] | Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Average remaining service period, in years		14 years
Duke Energy Indiana [Member] | Pension Plan [Member] | Nonqualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Average remaining service period, in years		8 years
Duke Energy Indiana [Member] | Other Post-Retirement Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Average remaining service period, in years		6 years
Piedmont Natural Gas [Member] | Pension Plan [Member] | Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Average remaining service period, in years		9 years
Expected long-term rate of return on plan assets	6.75%			7.25%		7.50%
Piedmont Natural Gas [Member] | Pension Plan [Member] | Nonqualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Average remaining service period, in years		9 years
Piedmont Natural Gas [Member] | Other Post-Retirement Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Average remaining service period, in years		7 years
Expected long-term rate of return on plan assets	6.75%			7.25%		7.50%