Fair Value Measurements (Other Fair Value Disclosures) (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt, fair value	$ 54,534	$ 55,331
Long-term Debt	54,529	52,279
Unamortized debt discount and premium, net	1,600	1,700
Duke Energy Carolinas [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt, fair value	11,471	11,372
Long-term Debt	10,939	10,103
Progress Energy [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt, fair value	19,885	20,000
Long-term Debt	18,911	17,837
Duke Energy Progress [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt, fair value	8,300	7,992
Long-term Debt	8,204	7,357
Duke Energy Florida [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt, fair value	7,742	7,953
Long-term Debt	7,321	7,095
Duke Energy Ohio [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt, fair value	2,239	2,249
Long-term Debt	2,165	2,067
Duke Energy Indiana [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt, fair value	4,158	4,464
Long-term Debt	3,782	3,783
Piedmont Natural Gas [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt, fair value	2,180	2,209
Long-term Debt	$ 2,138	$ 2,037