Acquisitions - Pro Forma Financial Information (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
(Loss) earnings per share:
Revenues	$ (2,563.5)	$ (1,230.7)	$ (4,916.7)	$ (2,412.8)
Transaction costs			(3.0)
Depreciation and amortization	(49.2)	(29.5)	(97.2)	(58.5)
Interest expense	(31.5)	(14.9)	(64.0)	(28.4)
Income from continuing operations before income tax benefit	$ 120.3	$ (59.2)	$ 91.5	$ (38.9)
Effective tax rate (as percent)	27.30%	45.60%	17.30%	56.60%
Alon
Business Acquisition [Line Items]
Net revenues		$ 2,303.3		$ 4,623.5
Net (loss) income attributable to Delek		$ (17.9)		$ 15.5
(Loss) earnings per share:
Basic (in dollars per share)		$ (0.22)		$ 0.19
Diluted (in dollars per share)		$ (0.22)		$ 0.19
Common stock conversion rate			0.504
Alon | Parent Company's Equity Income Elimination Adjustment
(Loss) earnings per share:
Revenues		$ 46.5		$ 59.0
Transaction costs		5.8		11.5
Depreciation and amortization		16.9		34.7
Accretion Expense, Including Asset Retirement Obligations		0.4		0.8
Interest expense		6.2		9.4
Income from continuing operations before income tax benefit		$ 0.4		$ 3.2
Alon | Tax Effect Adjustment
(Loss) earnings per share:
Effective tax rate (as percent)				36.58%