Fair Value Measurements (Quantitative Level 3 Fair Value Disclosure - Assets) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2018 USD ($) $ / MWh	Dec. 31, 2017 USD ($) $ / MWh	Dec. 31, 2016 USD ($)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Net Derivative Asset (Liability)	$ (113)	$ (114)	$ (166)
Duke Energy Ohio [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Net Derivative Asset (Liability)	6	1	5
Duke Energy Ohio [Member] | Financial Transmission Rights [Member] | Valuation, Market Approach [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Net Derivative Asset (Liability)	$ 6	$ 1
Duke Energy Ohio [Member] | Financial Transmission Rights [Member] | Minimum [Member] | Valuation, Market Approach [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value Input Price Per Unit | $ / MWh	1.19	0.07
Duke Energy Ohio [Member] | Financial Transmission Rights [Member] | Maximum [Member] | Valuation, Market Approach [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value Input Price Per Unit | $ / MWh	4.59	1.41
Duke Energy Indiana [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Net Derivative Asset (Liability)	$ 22	$ 27	$ 16
Duke Energy Indiana [Member] | Financial Transmission Rights [Member] | Valuation, Market Approach [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Net Derivative Asset (Liability)	$ 22	$ 27
Duke Energy Indiana [Member] | Financial Transmission Rights [Member] | Minimum [Member] | Valuation, Market Approach [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value Input Price Per Unit | $ / MWh	(2.07)	(0.77)
Duke Energy Indiana [Member] | Financial Transmission Rights [Member] | Maximum [Member] | Valuation, Market Approach [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value Input Price Per Unit | $ / MWh	8.27	7.44