Fair Value Measurements Significant Unobservable Inputs (Details) (Significant Unobservable Inputs (Level 3) [Member], USD $)
In Millions, except Per Share data, unless otherwise specified |
12 Months Ended |
---|---|
Dec. 31, 2012
|
|
Option Contracts, Gas [Member] | Options Models, Valuation Technique [Member]
|
|
Fair Value Inputs, Assets, Quantitative Information [Line Items] | |
Assets, Fair Value Disclosure | 42 |
Liabilities, Fair Value Disclosure | (18) |
Option Contracts, Gas [Member] | Implied Volatilities [Member] | Maximum [Member] | Options Models, Valuation Technique [Member]
|
|
Fair Value Inputs, Assets, Quantitative Information [Line Items] | |
Fair Value Inputs, Expected Rates | 39.00% |
Option Contracts, Gas [Member] | Implied Volatilities [Member] | Minimum [Member] | Options Models, Valuation Technique [Member]
|
|
Fair Value Inputs, Assets, Quantitative Information [Line Items] | |
Fair Value Inputs, Expected Rates | 1.00% |
Option Contracts, Gas [Member] | Implied Correlations [Member] | Maximum [Member] | Options Models, Valuation Technique [Member]
|
|
Fair Value Inputs, Assets, Quantitative Information [Line Items] | |
Fair Value Inputs, Expected Rates | 98.00% |
Option Contracts, Gas [Member] | Implied Correlations [Member] | Minimum [Member] | Options Models, Valuation Technique [Member]
|
|
Fair Value Inputs, Assets, Quantitative Information [Line Items] | |
Fair Value Inputs, Expected Rates | 12.00% |
Full Requirements and Unit Contingent Contracts [Member] | Discounted Cash Flow Valuation Technique [Member]
|
|
Fair Value Inputs, Assets, Quantitative Information [Line Items] | |
Assets, Fair Value Disclosure | 213 |
Liabilities, Fair Value Disclosure | (34) |
Full Requirements and Unit Contingent Contracts [Member] | Customer Migration Rate [Member] | Maximum [Member] | Discounted Cash Flow Valuation Technique [Member]
|
|
Fair Value Inputs, Assets, Quantitative Information [Line Items] | |
Fair Value Inputs, Expected Rates | 20.00% |
Full Requirements and Unit Contingent Contracts [Member] | Customer Migration Rate [Member] | Minimum [Member] | Discounted Cash Flow Valuation Technique [Member]
|
|
Fair Value Inputs, Assets, Quantitative Information [Line Items] | |
Fair Value Inputs, Expected Rates | 0.00% |
Full Requirements and Unit Contingent Contracts [Member] | Foward Price [Member] | Maximum [Member] | Discounted Cash Flow Valuation Technique [Member]
|
|
Fair Value Inputs, Assets, Quantitative Information [Line Items] | |
Fair Value Inputs, Offered Quotes | 122 |
Full Requirements and Unit Contingent Contracts [Member] | Foward Price [Member] | Minimum [Member] | Discounted Cash Flow Valuation Technique [Member]
|
|
Fair Value Inputs, Assets, Quantitative Information [Line Items] | |
Fair Value Inputs, Offered Quotes | 5 |
Option Contracts, Power [Member] | Options Models, Valuation Technique [Member]
|
|
Fair Value Inputs, Assets, Quantitative Information [Line Items] | |
Assets, Fair Value Disclosure | 112 |
Liabilities, Fair Value Disclosure | (72) |
Option Contracts, Power [Member] | Implied Volatilities [Member] | Maximum [Member] | Options Models, Valuation Technique [Member]
|
|
Fair Value Inputs, Assets, Quantitative Information [Line Items] | |
Fair Value Inputs, Expected Rates | 274.00% |
Option Contracts, Power [Member] | Implied Volatilities [Member] | Minimum [Member] | Options Models, Valuation Technique [Member]
|
|
Fair Value Inputs, Assets, Quantitative Information [Line Items] | |
Fair Value Inputs, Expected Rates | 1.00% |
Option Contracts, Power [Member] | Implied Correlations [Member] | Maximum [Member] | Options Models, Valuation Technique [Member]
|
|
Fair Value Inputs, Assets, Quantitative Information [Line Items] | |
Fair Value Inputs, Expected Rates | 98.00% |
Option Contracts, Power [Member] | Implied Correlations [Member] | Minimum [Member] | Options Models, Valuation Technique [Member]
|
|
Fair Value Inputs, Assets, Quantitative Information [Line Items] | |
Fair Value Inputs, Expected Rates | 12.00% |
Forward Contracts [Member] | Discounted Cash Flow Valuation Technique [Member]
|
|
Fair Value Inputs, Assets, Quantitative Information [Line Items] | |
Assets, Fair Value Disclosure | 399 |
Liabilities, Fair Value Disclosure | (88) |
Forward Contracts [Member] | Foward Price [Member] | Maximum [Member] | Discounted Cash Flow Valuation Technique [Member]
|
|
Fair Value Inputs, Assets, Quantitative Information [Line Items] | |
Fair Value Inputs, Offered Quotes | 184 |
Forward Contracts [Member] | Foward Price [Member] | Minimum [Member] | Discounted Cash Flow Valuation Technique [Member]
|
|
Fair Value Inputs, Assets, Quantitative Information [Line Items] | |
Fair Value Inputs, Offered Quotes | 9 |