Fair Value Measurements (Quantitative Level 3 Fair Value Disclosure) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 31, 2015	Dec. 31, 2014	Mar. 31, 2014	Dec. 31, 2013
Net Derivative Asset (Liability) Fair Value Inputs [Line Items]
Net derivative asset (liability)	$ 14	$ (1)	$ (14)	$ 13
Commodity Natural Gas Hedges [Member] | Discounted Cash Flow [Member]
Net Derivative Asset (Liability) Fair Value Inputs [Line Items]
Net derivative asset (liability)	11	(5)
Commodity Natural Gas Hedges [Member] | Minimum [Member] | Discounted Cash Flow [Member]
Net Derivative Asset (Liability) Fair Value Inputs [Line Items]
Fair Value Inputs Price Per MMBtu	1.96	2.12
Commodity Natural Gas Hedges [Member] | Maximum [Member] | Discounted Cash Flow [Member]
Net Derivative Asset (Liability) Fair Value Inputs [Line Items]
Fair Value Inputs Price Per MMBtu	3.78	4.35
Financial Transmission Rights [Member] | RTO Auction Pricing [Member]
Net Derivative Asset (Liability) Fair Value Inputs [Line Items]
Net derivative asset (liability)	3	14
Financial Transmission Rights [Member] | Minimum [Member] | RTO Auction Pricing [Member]
Net Derivative Asset (Liability) Fair Value Inputs [Line Items]
Fair value inputs, price per MWh	(0.83)	(1.92)
Financial Transmission Rights [Member] | Maximum [Member] | RTO Auction Pricing [Member]
Net Derivative Asset (Liability) Fair Value Inputs [Line Items]
Fair value inputs, price per MWh	8.47	9.86
Commodity Power Contracts [Member] | Discounted Cash Flow [Member]
Net Derivative Asset (Liability) Fair Value Inputs [Line Items]
Net derivative asset (liability)	8	(1)
Commodity Power Contracts [Member] | Minimum [Member] | Discounted Cash Flow [Member]
Net Derivative Asset (Liability) Fair Value Inputs [Line Items]
Fair value inputs, price per MWh	24.96	25.16
Commodity Power Contracts [Member] | Maximum [Member] | Discounted Cash Flow [Member]
Net Derivative Asset (Liability) Fair Value Inputs [Line Items]
Fair value inputs, price per MWh	51.33	51.75
Commodity Capacity Option Contracts [Member] | Discounted Cash Flow [Member]
Net Derivative Asset (Liability) Fair Value Inputs [Line Items]
Net derivative asset (liability)	1	2
Commodity Capacity Option Contracts [Member] | Minimum [Member] | Discounted Cash Flow [Member]
Net Derivative Asset (Liability) Fair Value Inputs [Line Items]
Fair Value Inputs Price Per MW day	19.00	21.00
Commodity Capacity Option Contracts [Member] | Maximum [Member] | Discounted Cash Flow [Member]
Net Derivative Asset (Liability) Fair Value Inputs [Line Items]
Fair Value Inputs Price Per MW day	109.50	109.00
Derivative Financial Instruments Liabilities Reserves [Member]
Net Derivative Asset (Liability) Fair Value Inputs [Line Items]
Net derivative asset (liability)	(9)	(11)
Duke Energy Carolinas [Member]
Net Derivative Asset (Liability) Fair Value Inputs [Line Items]
Net derivative asset (liability)			(4)	(2)
Progress Energy [Member]
Net Derivative Asset (Liability) Fair Value Inputs [Line Items]
Net derivative asset (liability)			(3)
Duke Energy Progress [Member]
Net Derivative Asset (Liability) Fair Value Inputs [Line Items]
Net derivative asset (liability)			(3)
Duke Energy Ohio [Member]
Net Derivative Asset (Liability) Fair Value Inputs [Line Items]
Net derivative asset (liability)	7	(18)	(19)	(4)
Duke Energy Ohio [Member] | Commodity Natural Gas Hedges [Member] | Discounted Cash Flow [Member]
Net Derivative Asset (Liability) Fair Value Inputs [Line Items]
Net derivative asset (liability)	11	(5)
Duke Energy Ohio [Member] | Commodity Natural Gas Hedges [Member] | Minimum [Member] | Discounted Cash Flow [Member]
Net Derivative Asset (Liability) Fair Value Inputs [Line Items]
Fair Value Inputs Price Per MMBtu	1.96	2.12
Duke Energy Ohio [Member] | Commodity Natural Gas Hedges [Member] | Maximum [Member] | Discounted Cash Flow [Member]
Net Derivative Asset (Liability) Fair Value Inputs [Line Items]
Fair Value Inputs Price Per MMBtu	3.78	4.35
Duke Energy Ohio [Member] | Commodity Power Contracts [Member] | Discounted Cash Flow [Member]
Net Derivative Asset (Liability) Fair Value Inputs [Line Items]
Net derivative asset (liability)	2	(6)
Duke Energy Ohio [Member] | Commodity Power Contracts [Member] | Minimum [Member] | Discounted Cash Flow [Member]
Net Derivative Asset (Liability) Fair Value Inputs [Line Items]
Fair value inputs, price per MWh	25.05	25.25
Duke Energy Ohio [Member] | Commodity Power Contracts [Member] | Maximum [Member] | Discounted Cash Flow [Member]
Net Derivative Asset (Liability) Fair Value Inputs [Line Items]
Fair value inputs, price per MWh	51.33	51.75
Duke Energy Ohio [Member] | Derivative Financial Instruments Liabilities Reserves [Member]
Net Derivative Asset (Liability) Fair Value Inputs [Line Items]
Net derivative asset (liability)	(6)	(7)
Duke Energy Indiana [Member]
Net Derivative Asset (Liability) Fair Value Inputs [Line Items]
Net derivative asset (liability)	3	14	7	12
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)	$ 3	$ 14
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 per MWh	(0.83)	(1.92)
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 per MWh	8.47	9.86