v2.4.0.6

Derivative Instruments (Gross Derivative Contract Positions Outstanding Relating To Energy And Weather Derivatives Trading Activities) (Details) | Mar. 31, 2013 MMBTU | Dec. 31, 2012 MMBTU
--- | --- | ---
Energy [Member] |  |  |  |
Derivative [Line Items] |  |  |  |
Derivative, Nonmonetary Notional Amount | 106,602,407 | [1] | 107,521,592 | [1]
Temperature [Member] |  |  |  |
Derivative [Line Items] |  |  |  |
Derivative, Notional Amount Per Unit | 4,246,626 | [1] | 8,168,052 | [1]
Precipitation [Member] |  |  |  |
Derivative [Line Items] |  |  |  |
Derivative, Notional Amount Per Unit | 4,808,787 | [1] | 4,453,934 | [1]
[1] | Represents the sum of gross long and gross short derivative contracts.

X
- Definition Aggregate notional amount of derivative expressed in nonmonetary units. For example, the number of barrels specified in a fuel oil forward purchase contract. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Article 12 -Section 13 -Sentence Column B + Details
Name: | invest_DerivativeNonmonetaryNotionalAmount
Namespace Prefix: | invest_
Data Type: | xbrli:decimalItemType
Balance Type: | na
Period Type: | instant

X
- Details
Name: | us-gaap_DerivativeLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The price per unit of the notional amount of the derivative contract expressed in nonmonetary units. For example, the price per barrel specified in a fuel oil forward purchase contract. + References No definition available. + Details
Name: | us-gaap_DerivativeNonmonetaryNotionalAmountPricePerUnit
Namespace Prefix: | us-gaap_
Data Type: | us-types:perUnitItemType
Balance Type: | na
Period Type: | instant