Severance (Expenses) (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
Restructuring Cost and Reserve [Line Items]
Severance expense		$ 15,000,000	$ 118,000,000		$ 142,000,000
Duke Energy Carolinas [Member]
Restructuring Cost and Reserve [Line Items]
Severance expense		2,000,000	39,000,000		93,000,000
Progress Energy [Member]
Restructuring Cost and Reserve [Line Items]
Severance expense		2,000,000	40,000,000		36,000,000
Duke Energy Progress [Member]
Restructuring Cost and Reserve [Line Items]
Severance expense		1,000,000	23,000,000		28,000,000
Duke Energy Florida [Member]
Restructuring Cost and Reserve [Line Items]
Severance expense		1,000,000	17,000,000		8,000,000
Duke Energy Ohio [Member]
Restructuring Cost and Reserve [Line Items]
Severance expense			3,000,000		2,000,000
Duke Energy Indiana [Member]
Restructuring Cost and Reserve [Line Items]
Severance expense		1,000,000	$ 7,000,000		$ 6,000,000
Piedmont Natural Gas [Member]
Restructuring Cost and Reserve [Line Items]
Severance expense	$ 3,000,000	$ 9,000,000		$ 19,000,000		$ 0