Fair Value (Details 3) (Significant unobservable inputs (Level 3), Embedded Derivatives in Commodity contracts)	6 Months Ended
	Jun. 30, 2014 period
Assets | Minimum
Unobservable inputs used in the valuation of Level 3 instruments of Assets
Forward ERCOT Pricing (per Megawatt Hour)	36.16
Assets | Maximum
Unobservable inputs used in the valuation of Level 3 instruments of Assets
Forward ERCOT Pricing (per Megawatt Hour)	52.42
Liabilities
Unobservable inputs used in the valuation of Level 3 instruments of Assets
Number of renewal periods	2
Term of counterparty option to renew gas purchase agreement	5 years
Probability of renewal (as a percent)	0.00%
Liabilities | Propane prices | Minimum
Unobservable inputs used in the valuation of Level 3 instruments of Assets
Forward price (in dollars per unit)	1.02
Liabilities | Propane prices | Maximum
Unobservable inputs used in the valuation of Level 3 instruments of Assets
Forward price (in dollars per unit)	1.10
Liabilities | Isobutane prices | Minimum
Unobservable inputs used in the valuation of Level 3 instruments of Assets
Forward price (in dollars per unit)	1.27
Liabilities | Isobutane prices | Maximum
Unobservable inputs used in the valuation of Level 3 instruments of Assets
Forward price (in dollars per unit)	1.38
Liabilities | Normal butane prices | Minimum
Unobservable inputs used in the valuation of Level 3 instruments of Assets
Forward price (in dollars per unit)	1.19
Liabilities | Normal butane prices | Maximum
Unobservable inputs used in the valuation of Level 3 instruments of Assets
Forward price (in dollars per unit)	1.32
Liabilities | Natural gasoline prices | Minimum
Unobservable inputs used in the valuation of Level 3 instruments of Assets
Forward price (in dollars per unit)	1.80
Liabilities | Natural gasoline prices | Maximum
Unobservable inputs used in the valuation of Level 3 instruments of Assets
Forward price (in dollars per unit)	2.21
Liabilities | Natural gas prices | Minimum
Unobservable inputs used in the valuation of Level 3 instruments of Assets
Forward price (in dollars per unit)	3.46
Liabilities | Natural gas prices | Maximum
Unobservable inputs used in the valuation of Level 3 instruments of Assets
Forward price (in dollars per unit)	5.14