Fair Value Measurements (Quantitative Level 3 Fair Value Disclosure) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2016 USD ($) $ / MWh	Dec. 31, 2015 USD ($) $ / MWh	Dec. 31, 2014 USD ($)
Net Derivative Asset (Liability) Fair Value Inputs [Line Items]
Net derivative asset (liability) | $	$ (166)	$ 10	$ (1)
Financial Transmission Rights [Member] | RTO Auction Pricing [Member]
Net Derivative Asset (Liability) Fair Value Inputs [Line Items]
Net derivative asset (liability) | $	$ 21	$ 10
Financial Transmission Rights [Member] | Minimum [Member] | RTO Auction Pricing [Member]
Net Derivative Asset (Liability) Fair Value Inputs [Line Items]
Fair value inputs, price FTR	(0.83)	(0.74)
Financial Transmission Rights [Member] | Maximum [Member] | RTO Auction Pricing [Member]
Net Derivative Asset (Liability) Fair Value Inputs [Line Items]
Fair value inputs, price FTR	9.32	7.29
Energy Related Derivative [Member] | Natural Gas, derivative liability [Member] | Discounted Cash Flow [Member]
Net Derivative Asset (Liability) Fair Value Inputs [Line Items]
Net derivative asset (liability) | $	$ (187)
Energy Related Derivative [Member] | Natural Gas, derivative liability [Member] | Minimum [Member] | Discounted Cash Flow [Member]
Net Derivative Asset (Liability) Fair Value Inputs [Line Items]
Fair value inputs, price FTR	2.31
Energy Related Derivative [Member] | Natural Gas, derivative liability [Member] | Maximum [Member] | Discounted Cash Flow [Member]
Net Derivative Asset (Liability) Fair Value Inputs [Line Items]
Fair value inputs, price FTR	4.18
Duke Energy Ohio [Member]
Net Derivative Asset (Liability) Fair Value Inputs [Line Items]
Net derivative asset (liability) | $	$ 5	$ 3	(18)
Duke Energy Ohio [Member] | Financial Transmission Rights [Member] | RTO Auction Pricing [Member]
Net Derivative Asset (Liability) Fair Value Inputs [Line Items]
Net derivative asset (liability) | $	$ 5	$ 3
Duke Energy Ohio [Member] | Financial Transmission Rights [Member] | Minimum [Member] | RTO Auction Pricing [Member]
Net Derivative Asset (Liability) Fair Value Inputs [Line Items]
Fair value inputs, price FTR	0.77	0.67
Duke Energy Ohio [Member] | Financial Transmission Rights [Member] | Maximum [Member] | RTO Auction Pricing [Member]
Net Derivative Asset (Liability) Fair Value Inputs [Line Items]
Fair value inputs, price FTR	3.52	2.53
Duke Energy Indiana [Member]
Net Derivative Asset (Liability) Fair Value Inputs [Line Items]
Net derivative asset (liability) | $	$ 16	$ 7	$ 14
Duke Energy Indiana [Member] | Financial Transmission Rights [Member] | RTO Auction Pricing [Member]
Net Derivative Asset (Liability) Fair Value Inputs [Line Items]
Net derivative asset (liability) | $	$ 16	$ 7
Duke Energy Indiana [Member] | Financial Transmission Rights [Member] | Minimum [Member] | RTO Auction Pricing [Member]
Net Derivative Asset (Liability) Fair Value Inputs [Line Items]
Fair value inputs, price FTR	(0.83)	(0.74)
Duke Energy Indiana [Member] | Financial Transmission Rights [Member] | Maximum [Member] | RTO Auction Pricing [Member]
Net Derivative Asset (Liability) Fair Value Inputs [Line Items]
Fair value inputs, price FTR	9.32	7.29