Derivative Instruments - Derivative Assets and Liabilities (Details) $ in Millions		Dec. 31, 2018 USD ($) bbl rins	Dec. 31, 2017 USD ($) bbl rins
Derivatives, Fair Value [Line Items]
Assets		$ 461.8	$ 179.4
Less: Counterparty netting and cash collateral, assets	[1]	399.9	163.5
Total net fair value of derivative assets		61.9	15.9
Liabilities		(415.7)	(228.8)
Less: Counterparty netting and cash collateral, liabilities	[1]	(399.5)	(173.6)
Total net fair value of derivative liabilities		(16.2)	(55.2)
Cash collateral		$ 0.4	$ 10.0
Commodity derivatives
Derivatives, Fair Value [Line Items]
Derivative open contract | bbl		39,277,822	35,978,000
Commodity derivatives | Derivatives not designated as hedging instruments: | Other current assets
Derivatives, Fair Value [Line Items]
Assets	[2]	$ 158.3	$ 164.6
Liabilities	[2]	(142.4)	(162.0)
Commodity derivatives | Derivatives not designated as hedging instruments: | Other current liabilities
Derivatives, Fair Value [Line Items]
Assets	[2]	0.0	13.4
Liabilities	[2]	(8.4)	(28.3)
Commodity derivatives | Derivatives not designated as hedging instruments: | Other long-term assets
Derivatives, Fair Value [Line Items]
Assets	[2]	2.1	0.0
Liabilities	[2]	(2.4)	0.0
Commodity derivatives | Derivatives not designated as hedging instruments: | Other long-term liabilities
Derivatives, Fair Value [Line Items]
Assets	[2]	93.0	0.0
Liabilities	[2]	$ (94.0)	$ 0.0
Commodity derivatives | Derivatives designated as hedging instruments:
Derivatives, Fair Value [Line Items]
Derivative open contract | bbl		16,461,000	575,000
Commodity derivatives | Derivatives designated as hedging instruments: | Other current assets
Derivatives, Fair Value [Line Items]
Assets	[2]	$ 200.3	$ 0.0
Liabilities	[2]	(157.0)	0.0
Commodity derivatives | Derivatives designated as hedging instruments: | Other current liabilities
Derivatives, Fair Value [Line Items]
Assets	[2]	0.0	0.0
Liabilities	[2]	0.0	(13.6)
Commodity derivatives | Derivatives designated as hedging instruments: | Other long-term assets
Derivatives, Fair Value [Line Items]
Assets	[2]	6.1	0.0
Liabilities	[2]	(4.8)	$ 0.0
RIN Commitment Contracts
Derivatives, Fair Value [Line Items]
Derivative open contract | rins			163,361,320
RIN Commitment Contracts | Derivatives not designated as hedging instruments: | Other current assets
Derivatives, Fair Value [Line Items]
Assets	[3]	2.0	$ 1.4
Liabilities	[3]	$ 0.0	0.0
Derivative open contract | rins		137,750,000
RIN Commitment Contracts | Derivatives not designated as hedging instruments: | Other current liabilities
Derivatives, Fair Value [Line Items]
Assets	[3]	$ 0.0	0.0
Liabilities	[3]	(6.7)	(24.0)
Interest rate derivatives | Derivatives designated as hedging instruments: | Other long-term liabilities
Derivatives, Fair Value [Line Items]
Assets		0.0	0.0
Liabilities		$ 0.0	$ (0.9)

[1] As of December 31, 2018 and 2017, $(0.4) million and $10.0 million, respectively, of cash (obligation) collateral held by counterparties has been netted with the derivatives with each counterparty.

[2] As of December 31, 2018 and 2017, we had open derivative positions representing 39,277,822 and 35,978,000 barrels, respectively, of crude oil and refined petroleum products. Of these open positions, contracts representing 16,461,000 and 575,000 barrels were designated as cash flow hedging instruments as of December 31, 2018 and 2017, respectively.

[3] As of December 31, 2018 and 2017, we had open RIN commitment contracts representing 137,750,000 and 163,361,320 RINs, respectively.