Derivative Instruments, Hedging Activities and Fair Value Measurements, Level 3 Recurring Valuation Techniques (Details) $ in Millions	12 Months Ended
	Dec. 31, 2018 USD ($) $ / bbl $ / gal	Dec. 31, 2017 USD ($) $ / bbl
Asset commodity derivatives - Crude oil [Member] | Liability commodity derivatives - Crude oil [Member] | Level 3 [Member] | Minimum [Member]
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Fair value inputs, forward commodity price (in dollars per unit) | $ / bbl	37.59	60.21
Asset commodity derivatives - Crude oil [Member] | Liability commodity derivatives - Crude oil [Member] | Level 3 [Member] | Maximum [Member]
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Fair value inputs, forward commodity price (in dollars per unit) | $ / bbl	51.99	66.05
Asset Commodity derivatives - Ethane [Member] | Liability Commodity Derivatives - Ethane [Member] | Level 3 [Member] | Minimum [Member]
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Fair value inputs, forward commodity price (in dollars per unit) | $ / gal	0.28
Asset Commodity derivatives - Ethane [Member] | Liability Commodity Derivatives - Ethane [Member] | Level 3 [Member] | Maximum [Member]
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Fair value inputs, forward commodity price (in dollars per unit) | $ / gal	0.31
Asset commodity derivatives - Propane [Member] | Liability commodity derivatives - Propane [Member] | Level 3 [Member] | Minimum [Member]
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Fair value inputs, forward commodity price (in dollars per unit) | $ / gal	0.61
Asset commodity derivatives - Propane [Member] | Liability commodity derivatives - Propane [Member] | Level 3 [Member] | Maximum [Member]
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Fair value inputs, forward commodity price (in dollars per unit) | $ / gal	0.66
Asset commodity derivatives - Normal butane [Member] | Liability commodity derivatives - Normal butane [Member] | Level 3 [Member] | Minimum [Member]
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Fair value inputs, forward commodity price (in dollars per unit) | $ / gal	0.66
Asset commodity derivatives - Normal butane [Member] | Liability commodity derivatives - Normal butane [Member] | Level 3 [Member] | Maximum [Member]
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Fair value inputs, forward commodity price (in dollars per unit) | $ / gal	0.72
Asset commodity derivatives - Natural gasoline [Member] | Liability commodity derivatives - Natural gasoline [Member] | Level 3 [Member] | Minimum [Member]
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Fair value inputs, forward commodity price (in dollars per unit) | $ / gal	0.99
Asset commodity derivatives - Natural gasoline [Member] | Liability commodity derivatives - Natural gasoline [Member] | Level 3 [Member] | Maximum [Member]
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Fair value inputs, forward commodity price (in dollars per unit) | $ / gal	1.01
Fair Value, Measurements, Recurring [Member]
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Commodity asset derivatives	$ 161.9	$ 161.7
Commodity liability derivatives	162.4	176.9
Fair Value, Measurements, Recurring [Member] | Level 3 [Member]
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Commodity asset derivatives	1.3	2.9
Commodity liability derivatives	7.2	1.7
Fair Value, Measurements, Recurring [Member] | Liability commodity derivatives - Crude oil [Member] | Level 3 [Member]
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Commodity liability derivatives	0.8	1.7
Fair Value, Measurements, Recurring [Member] | Liability Commodity Derivatives - Ethane [Member] | Level 3 [Member]
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Commodity liability derivatives	0.6
Fair Value, Measurements, Recurring [Member] | Liability commodity derivatives - Normal butane [Member] | Level 3 [Member]
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Commodity liability derivatives	0.7
Fair Value, Measurements, Recurring [Member] | Liability commodity derivatives - Natural gasoline [Member] | Level 3 [Member]
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Commodity liability derivatives	4.1
Fair Value, Measurements, Recurring [Member] | Liability commodity derivatives - Propane [Member] | Level 3 [Member]
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Commodity liability derivatives	1.0
Fair Value, Measurements, Recurring [Member] | Asset commodity derivatives - Crude oil [Member] | Level 3 [Member]
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Commodity asset derivatives	0.9	$ 2.9
Fair Value, Measurements, Recurring [Member] | Asset Commodity derivatives - Ethane [Member] | Level 3 [Member]
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Commodity asset derivatives	0.4
Fair Value, Measurements, Recurring [Member] | Asset commodity derivatives - Propane [Member] | Level 3 [Member]
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Commodity asset derivatives	0.0
Fair Value, Measurements, Recurring [Member] | Asset commodity derivatives - Normal butane [Member] | Level 3 [Member]
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Commodity asset derivatives	0.0
Fair Value, Measurements, Recurring [Member] | Asset commodity derivatives - Natural gasoline [Member] | Level 3 [Member]
Fair Value Measurements, Recurring, Valuation Techniques [Line Items]
Commodity asset derivatives	$ 0.0