Fair Value (Details 3)	6 Months Ended
	Jun. 30, 2013
Unobservable inputs used in the valuation of Level 3 instruments of assets
Term of counterparty option to renew gas purchase agreement	5 years
Embedded Derivatives in commodity contracts | Assets | Significant unobservable inputs (Level 3) | Minimum
Unobservable inputs used in the valuation of Level 3 instruments of Assets
Forward ERCOT Pricing (per MegaWatt Hour)	28.09
Embedded Derivatives in commodity contracts | Assets | Significant unobservable inputs (Level 3) | Maximum
Unobservable inputs used in the valuation of Level 3 instruments of Assets
Forward ERCOT Pricing (per MegaWatt Hour)	67.91
Embedded Derivatives in commodity contracts | Liabilities | Significant unobservable inputs (Level 3)
Unobservable inputs used in the valuation of Level 3 instruments of assets
Probability of renewal (as a percent)	0.00%
Number of renewal periods	2
Term of counterparty option to renew gas purchase agreement	5 years
Embedded Derivatives in commodity contracts | Propane prices | Liabilities | Significant unobservable inputs (Level 3) | Minimum
Unobservable inputs used in the valuation of Level 3 instruments of assets
Forward price (in dollars per unit)	0.78
Embedded Derivatives in commodity contracts | Propane prices | Liabilities | Significant unobservable inputs (Level 3) | Maximum
Unobservable inputs used in the valuation of Level 3 instruments of assets
Forward price (in dollars per unit)	0.88
Embedded Derivatives in commodity contracts | Isobutane prices | Liabilities | Significant unobservable inputs (Level 3) | Minimum
Unobservable inputs used in the valuation of Level 3 instruments of assets
Forward price (in dollars per unit)	1.13
Embedded Derivatives in commodity contracts | Isobutane prices | Liabilities | Significant unobservable inputs (Level 3) | Maximum
Unobservable inputs used in the valuation of Level 3 instruments of assets
Forward price (in dollars per unit)	1.24
Embedded Derivatives in commodity contracts | Normal butane prices | Liabilities | Significant unobservable inputs (Level 3) | Minimum
Unobservable inputs used in the valuation of Level 3 instruments of assets
Forward price (in dollars per unit)	1.03
Embedded Derivatives in commodity contracts | Normal butane prices | Liabilities | Significant unobservable inputs (Level 3) | Maximum
Unobservable inputs used in the valuation of Level 3 instruments of assets
Forward price (in dollars per unit)	1.20
Embedded Derivatives in commodity contracts | Natural gasoline prices | Liabilities | Significant unobservable inputs (Level 3) | Minimum
Unobservable inputs used in the valuation of Level 3 instruments of assets
Forward price (in dollars per unit)	1.66
Embedded Derivatives in commodity contracts | Natural gasoline prices | Liabilities | Significant unobservable inputs (Level 3) | Maximum
Unobservable inputs used in the valuation of Level 3 instruments of assets
Forward price (in dollars per unit)	1.98
Embedded Derivatives in commodity contracts | Natural gas prices | Liabilities | Significant unobservable inputs (Level 3) | Minimum
Unobservable inputs used in the valuation of Level 3 instruments of assets
Forward price (in dollars per unit)	3.38
Embedded Derivatives in commodity contracts | Natural gas prices | Liabilities | Significant unobservable inputs (Level 3) | Maximum
Unobservable inputs used in the valuation of Level 3 instruments of assets
Forward price (in dollars per unit)	6.42