Employee Benefit Plans (Employee Savings Plans)(Details) - USD ($)	2 Months Ended	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Oct. 31, 2016	Dec. 31, 2015	Oct. 31, 2015
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		$ 179,000,000	$ 169,000,000		$ 159,000,000
Duke Energy Carolinas [Member]
Employee Savings Plans [Abstract]
Employer contributions		61,000,000	57,000,000		54,000,000
Progress Energy [Member]
Employee Savings Plans [Abstract]
Employer contributions		53,000,000	50,000,000		48,000,000
Duke Energy Progress [Member]
Employee Savings Plans [Abstract]
Employer contributions		37,000,000	35,000,000		34,000,000
Duke Energy Florida [Member]
Employee Savings Plans [Abstract]
Employer contributions		16,000,000	15,000,000		13,000,000
Duke Energy Ohio [Member]
Employee Savings Plans [Abstract]
Employer contributions		3,000,000	3,000,000		3,000,000
Duke Energy Indiana [Member]
Employee Savings Plans [Abstract]
Employer contributions		$ 9,000,000	8,000,000		7,000,000
Piedmont Natural Gas [Member]
Employee Savings Plans [Abstract]
Eligible pay percentage		5.00%
Additional contribution percentage for employees not participating in defined pension plans		4.00%
Employer contributions			$ 0		$ 0
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		$ 2,000,000
Piedmont Natural Gas [Member] | 401K [Member]
Employee Savings Plans [Abstract]
Employer contributions	$ 1,000,000	$ 7,000,000		$ 7,000,000		$ 7,000,000