Employee Benefit Plans (Employee Savings Plans) (Details) - USD ($)	2 Months Ended	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Oct. 31, 2016
Employee Savings Plans [Abstract]
Matching contribution percentage		100.00%
Eligible pay percentage		6.00%
Additional contribution percentage for employees not participating in defined pension plans		4.00%
Employer contributions		$ 213,000,000	$ 179,000,000	$ 169,000,000
Duke Energy Carolinas [Member]
Employee Savings Plans [Abstract]
Employer contributions		68,000,000	61,000,000	57,000,000
Progress Energy [Member]
Employee Savings Plans [Abstract]
Employer contributions		58,000,000	53,000,000	50,000,000
Duke Energy Progress [Member]
Employee Savings Plans [Abstract]
Employer contributions		40,000,000	37,000,000	35,000,000
Duke Energy Florida [Member]
Employee Savings Plans [Abstract]
Employer contributions		19,000,000	16,000,000	15,000,000
Duke Energy Ohio [Member]
Employee Savings Plans [Abstract]
Employer contributions		4,000,000	3,000,000	3,000,000
Duke Energy Indiana [Member]
Employee Savings Plans [Abstract]
Employer contributions		$ 10,000,000	9,000,000	8,000,000
Piedmont Natural Gas [Member]
Employee Savings Plans [Abstract]
Additional contribution percentage for employees not participating in defined pension plans		4.00%
Employer contributions			7,000,000
Piedmont Natural Gas [Member] | Pension Plan [Member]
Employee Savings Plans [Abstract]
Eligible pay percentage		4.00%
Employer contributions	$ 0		$ 2,000,000		$ 2,000,000
Piedmont Natural Gas [Member] | 401K [Member]
Employee Savings Plans [Abstract]
Employer contributions	$ 1,000,000	$ 12,000,000			$ 7,000,000