Fair Value (Details 2) (Commodity contracts, Significant unobservable inputs (Level 3))	6 Months Ended
	Jun. 30, 2013
Assets | Minimum
Unobservable inputs used in the valuation of Level 3 instruments of Assets and Liabilities
Crude option volatilities (as a percent)	12.49%
Propane option volatilities (as a percent)	13.33%
Assets | Maximum
Unobservable inputs used in the valuation of Level 3 instruments of Assets and Liabilities
Crude option volatilities (as a percent)	24.48%
Propane option volatilities (as a percent)	22.49%
Assets | Propane prices | Minimum
Unobservable inputs used in the valuation of Level 3 instruments of Assets and Liabilities
Forward price (in dollars per unit)	0.82
Assets | Propane prices | Maximum
Unobservable inputs used in the valuation of Level 3 instruments of Assets and Liabilities
Forward price (in dollars per unit)	0.88
Assets | Isobutane prices | Minimum
Unobservable inputs used in the valuation of Level 3 instruments of Assets and Liabilities
Forward price (in dollars per unit)	1.19
Assets | Isobutane prices | Maximum
Unobservable inputs used in the valuation of Level 3 instruments of Assets and Liabilities
Forward price (in dollars per unit)	1.24
Assets | Normal butane prices | Minimum
Unobservable inputs used in the valuation of Level 3 instruments of Assets and Liabilities
Forward price (in dollars per unit)	1.08
Assets | Normal butane prices | Maximum
Unobservable inputs used in the valuation of Level 3 instruments of Assets and Liabilities
Forward price (in dollars per unit)	1.20
Assets | Natural gasoline prices | Minimum
Unobservable inputs used in the valuation of Level 3 instruments of Assets and Liabilities
Forward price (in dollars per unit)	1.84
Assets | Natural gasoline prices | Maximum
Unobservable inputs used in the valuation of Level 3 instruments of Assets and Liabilities
Forward price (in dollars per unit)	1.98
Liabilities | Minimum
Unobservable inputs used in the valuation of Level 3 instruments of Assets and Liabilities
Crude option volatilities (as a percent)	11.75%
Liabilities | Maximum
Unobservable inputs used in the valuation of Level 3 instruments of Assets and Liabilities
Crude option volatilities (as a percent)	24.92%
Liabilities | Propane prices | Minimum
Unobservable inputs used in the valuation of Level 3 instruments of Assets and Liabilities
Forward price (in dollars per unit)	0.82
Liabilities | Propane prices | Maximum
Unobservable inputs used in the valuation of Level 3 instruments of Assets and Liabilities
Forward price (in dollars per unit)	0.85
Liabilities | Isobutane prices | Minimum
Unobservable inputs used in the valuation of Level 3 instruments of Assets and Liabilities
Forward price (in dollars per unit)	1.19
Liabilities | Isobutane prices | Maximum
Unobservable inputs used in the valuation of Level 3 instruments of Assets and Liabilities
Forward price (in dollars per unit)	1.22
Liabilities | Normal butane prices | Minimum
Unobservable inputs used in the valuation of Level 3 instruments of Assets and Liabilities
Forward price (in dollars per unit)	1.08
Liabilities | Normal butane prices | Maximum
Unobservable inputs used in the valuation of Level 3 instruments of Assets and Liabilities
Forward price (in dollars per unit)	1.20
Liabilities | Natural gasoline prices | Minimum
Unobservable inputs used in the valuation of Level 3 instruments of Assets and Liabilities
Forward price (in dollars per unit)	1.93
Liabilities | Natural gasoline prices | Maximum
Unobservable inputs used in the valuation of Level 3 instruments of Assets and Liabilities
Forward price (in dollars per unit)	1.98