Summary of Significant Accounting Policies (Property, Plant and Equipment)(Details)	2 Months Ended	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Oct. 31, 2016	Dec. 31, 2015	Oct. 31, 2015
Public Utility, Property, Plant and Equipment [Line Items]
Weighted-average depreciation rate		2.80%	2.80%		2.90%
Duke Energy Carolinas [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Weighted-average depreciation rate		2.80%	2.80%		2.80%
Progress Energy [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Weighted-average depreciation rate		2.60%	2.70%		2.60%
Duke Energy Progress [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Weighted-average depreciation rate		2.60%	2.60%		2.60%
Duke Energy Florida [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Weighted-average depreciation rate		2.80%	2.80%		2.70%
Duke Energy Ohio [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Weighted-average depreciation rate		2.80%	2.60%		2.70%
Duke Energy Indiana [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Weighted-average depreciation rate		3.00%	3.10%		3.00%
Piedmont Natural Gas [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Weighted-average depreciation rate	2.40%	2.30%		2.40%		2.50%