Fair Value (Details 3) (Embedded Derivatives in Commodity Contracts (net), Significant unobservable inputs (Level 3))	9 Months Ended
	Sep. 30, 2013 item
Assets | Minimum
Unobservable inputs used in the valuation of Level 3 instruments of Assets
Forward ERCOT Pricing (per MegaWatt Hour)	29.19
Assets | Maximum
Unobservable inputs used in the valuation of Level 3 instruments of Assets
Forward ERCOT Pricing (per MegaWatt Hour)	58.68
Liabilities
Unobservable inputs used in the valuation of Level 3 instruments of Assets and Liabilities
Probability of renewal (as a percent)	0.00%
Number of renewal periods	2
Term of counterparty option to renew gas purchase agreement	5 years
Propane prices | Liabilities | Minimum
Unobservable inputs used in the valuation of Level 3 instruments of Assets and Liabilities
Forward price (in dollars per unit)	0.89
Propane prices | Liabilities | Maximum
Unobservable inputs used in the valuation of Level 3 instruments of Assets and Liabilities
Forward price (in dollars per unit)	1.07
Isobutane prices | Liabilities | Minimum
Unobservable inputs used in the valuation of Level 3 instruments of Assets and Liabilities
Forward price (in dollars per unit)	1.26
Isobutane prices | Liabilities | Maximum
Unobservable inputs used in the valuation of Level 3 instruments of Assets and Liabilities
Forward price (in dollars per unit)	1.41
Normal butane prices | Liabilities | Minimum
Unobservable inputs used in the valuation of Level 3 instruments of Assets and Liabilities
Forward price (in dollars per unit)	1.14
Normal butane prices | Liabilities | Maximum
Unobservable inputs used in the valuation of Level 3 instruments of Assets and Liabilities
Forward price (in dollars per unit)	1.38
Natural gasoline prices | Liabilities | Minimum
Unobservable inputs used in the valuation of Level 3 instruments of Assets and Liabilities
Forward price (in dollars per unit)	1.73
Natural gasoline prices | Liabilities | Maximum
Unobservable inputs used in the valuation of Level 3 instruments of Assets and Liabilities
Forward price (in dollars per unit)	2.07
Natural gas prices | Liabilities | Minimum
Unobservable inputs used in the valuation of Level 3 instruments of Assets and Liabilities
Forward price (in dollars per unit)	3.50
Natural gas prices | Liabilities | Maximum
Unobservable inputs used in the valuation of Level 3 instruments of Assets and Liabilities
Forward price (in dollars per unit)	5.50