Derivative Instruments, Hedging Activities and Fair Value Measurements, Level 3 Recurring Valuation Techniques (Details) (Level 3 [Member], USD $) In Millions, unless otherwise specified	9 Months Ended
	Sep. 30, 2013
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Asset commodity derivatives	$ 2.3
Liability commodity derivatives	2.2
Liability commodity derivatives - Crude oil [Member]
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Liability commodity derivatives	0.2
Liability commodity derivatives - Normal butane [Member]
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Liability commodity derivatives	0.1
Liability commodity derivatives - Natural gasoline [Member]
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Liability commodity derivatives	1.4
Liability commodity derivatives - Natural gas [Member]
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Liability commodity derivatives	0.5
Liability commodity derivatives - Propane [Member]
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Liability commodity derivatives	0
Asset commodity derivatives - Propane [Member]
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Asset commodity derivatives	0.1
Asset commodity derivatives - Propane [Member] | Liability commodity derivatives - Propane [Member]
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Fair Value Measurements, Valuation Techniques	Discounted cash flow
Input description	Forward commodity prices
Asset commodity derivatives - Propane [Member] | Liability commodity derivatives - Propane [Member] | Minimum [Member]
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Fair value inputs, forward commodity price (in dollars per unit)	0.97
Asset commodity derivatives - Propane [Member] | Liability commodity derivatives - Propane [Member] | Maximum [Member]
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Fair value inputs, forward commodity price (in dollars per unit)	1.07
Asset commodity derivatives - Normal butane [Member]
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Asset commodity derivatives	0
Asset commodity derivatives - Normal butane [Member] | Liability commodity derivatives - Normal butane [Member]
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Fair Value Measurements, Valuation Techniques	Discounted cash flow
Input description	Forward commodity prices
Asset commodity derivatives - Normal butane [Member] | Liability commodity derivatives - Normal butane [Member] | Minimum [Member]
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Fair value inputs, forward commodity price (in dollars per unit)	1.26
Asset commodity derivatives - Normal butane [Member] | Liability commodity derivatives - Normal butane [Member] | Maximum [Member]
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Fair value inputs, forward commodity price (in dollars per unit)	1.38
Asset commodity derivatives - Crude oil [Member]
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Asset commodity derivatives	1.4
Asset commodity derivatives - Crude oil [Member] | Liability commodity derivatives - Crude oil [Member]
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Fair Value Measurements, Valuation Techniques	Discounted cash flow
Input description	Forward commodity prices
Asset commodity derivatives - Crude oil [Member] | Liability commodity derivatives - Crude oil [Member] | Minimum [Member]
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Fair value inputs, forward commodity price (in dollars per unit)	91.87
Asset commodity derivatives - Crude oil [Member] | Liability commodity derivatives - Crude oil [Member] | Maximum [Member]
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Fair value inputs, forward commodity price (in dollars per unit)	103.07
Assets commodity derivatives - Natural gas [Member]
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Asset commodity derivatives	0.2
Assets commodity derivatives - Natural gas [Member] | Liability commodity derivatives - Natural gas [Member]
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Fair Value Measurements, Valuation Techniques	Discounted cash flow
Input description	Forward commodity prices
Assets commodity derivatives - Natural gas [Member] | Liability commodity derivatives - Natural gas [Member] | Minimum [Member]
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Fair value inputs, forward commodity price (in dollars per unit)	3.26
Assets commodity derivatives - Natural gas [Member] | Liability commodity derivatives - Natural gas [Member] | Maximum [Member]
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Fair value inputs, forward commodity price (in dollars per unit)	3.99
Asset commodity derivatives - Natural gasoline [Member]
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Asset commodity derivatives	$ 0.6
Asset commodity derivatives - Natural gasoline [Member] | Liability commodity derivatives - Natural gasoline [Member]
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Fair Value Measurements, Valuation Techniques	Discounted cash flow
Input description	Forward commodity prices
Asset commodity derivatives - Natural gasoline [Member] | Liability commodity derivatives - Natural gasoline [Member] | Minimum [Member]
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Fair value inputs, forward commodity price (in dollars per unit)	1.92
Asset commodity derivatives - Natural gasoline [Member] | Liability commodity derivatives - Natural gasoline [Member] | Maximum [Member]
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Fair value inputs, forward commodity price (in dollars per unit)	2.07