Fair Value Measurements (Significant Unobservable Inputs Used in Valuation of Contracts) (Details) (Level 3 [Member], USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2014
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Assets, Fair Value Disclosure	$ 1,035
Liabilities, Fair Value Disclosure	467
Forward Contracts - power [Member] | Discounted Cash Flow Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Assets, Fair Value Disclosure	605
Liabilities, Fair Value Disclosure	106
Forward Contracts - power [Member] | Discounted Cash Flow Member] | Foward Price [Member] | Minimum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Expected rates (in dollars per unit)	$ 9
Forward Contracts - power [Member] | Discounted Cash Flow Member] | Foward Price [Member] | Maximum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Expected rates (in dollars per unit)	$ 156
Forward contracts - Gas [Member] | Discounted Cash Flow Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Assets, Fair Value Disclosure	96
Liabilities, Fair Value Disclosure	44
Forward contracts - Gas [Member] | Discounted Cash Flow Member] | Foward Price [Member] | Minimum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Expected rates (in dollars per unit)	$ 2
Forward contracts - Gas [Member] | Discounted Cash Flow Member] | Foward Price [Member] | Maximum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Expected rates (in dollars per unit)	$ 16
Forward contracts - other commodity related [Member] | Discounted Cash Flow Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Assets, Fair Value Disclosure	23
Liabilities, Fair Value Disclosure	16
Forward contracts - other commodity related [Member] | Discounted Cash Flow Member] | Foward Price [Member] | Minimum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Expected rates (in dollars per unit)	$ 1
Forward contracts - other commodity related [Member] | Discounted Cash Flow Member] | Foward Price [Member] | Maximum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Expected rates (in dollars per unit)	$ 245
Options - Power [Member] | Option Models [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Assets, Fair Value Disclosure	79
Liabilities, Fair Value Disclosure	84
Options - Power [Member] | Option Models [Member] | Implied Correlations [Member] | Minimum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Expected rates (as a percentage)	7.00%
Options - Power [Member] | Option Models [Member] | Implied Correlations [Member] | Maximum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Expected rates (as a percentage)	96.00%
Options - Power [Member] | Option Models [Member] | Implied Volatilities [Member] | Minimum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Expected rates (as a percentage)	1.00%
Options - Power [Member] | Option Models [Member] | Implied Volatilities [Member] | Maximum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Expected rates (as a percentage)	271.00%
Options - Gas [Member] | Option Models [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Assets, Fair Value Disclosure	34
Liabilities, Fair Value Disclosure	57
Options - Gas [Member] | Option Models [Member] | Implied Correlations [Member] | Minimum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Expected rates (as a percentage)	7.00%
Options - Gas [Member] | Option Models [Member] | Implied Correlations [Member] | Maximum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Expected rates (as a percentage)	96.00%
Options - Gas [Member] | Option Models [Member] | Implied Volatilities [Member] | Minimum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Expected rates (as a percentage)	1.00%
Options - Gas [Member] | Option Models [Member] | Implied Volatilities [Member] | Maximum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Expected rates (as a percentage)	70.00%
Full Requirements and Unit Contingent Contracts [Member] | Discounted Cash Flow Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Assets, Fair Value Disclosure	198
Liabilities, Fair Value Disclosure	160
Full Requirements and Unit Contingent Contracts [Member] | Discounted Cash Flow Member] | Foward Price [Member] | Minimum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Expected rates (in dollars per unit)	$ (10)
Full Requirements and Unit Contingent Contracts [Member] | Discounted Cash Flow Member] | Foward Price [Member] | Maximum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Expected rates (in dollars per unit)	$ 203
Full Requirements and Unit Contingent Contracts [Member] | Discounted Cash Flow Member] | Customer Migration Rate [Member] | Minimum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Expected rates (as a percentage)	0.00%	[1]
Full Requirements and Unit Contingent Contracts [Member] | Discounted Cash Flow Member] | Customer Migration Rate [Member] | Maximum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Expected rates (as a percentage)	20.00%	[1]
NextEra Energy Resources [Member] | Interest rate contracts [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Liabilities, Fair Value Disclosure	$ 108

[1] Applies only to full requirements contracts.