Acquisitions - Schedule of Pro Forma Information (Details) $ / shares in Units, $ in Millions		3 Months Ended								12 Months Ended
	Jul. 01, 2017	Dec. 31, 2019 USD ($)	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($) $ / shares
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Revenues		$ 2,283.7	$ 2,334.3	$ 2,480.3	$ 2,199.9	$ 2,474.1	$ 2,768.9	$ 2,636.9	$ 2,353.2	$ 9,298.2	$ 10,233.1	$ 7,267.1
Acquisition related transaction costs											3.0
Depreciation and amortization										23.6	38.1	21.2
Accretion expense										1.7	1.9
Interest expense										131.1	125.9	93.8
Income (loss) from continuing operations before income tax expense										$ 402.7	$ 485.5	299.3
Alon USA Energy, Inc.
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Net revenues												9,477.8
Net income attributable to Delek												$ 223.6
Basic (USD per share) | $ / shares												$ 2.75
Diluted (USD per share) | $ / shares												$ 2.73
Alon USA Energy, Inc. | Parent Company's Equity Income Elimination Adjustment
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Revenues												$ (59.0)
Acquisition related transaction costs												(32.2)
Depreciation and amortization												(34.7)
Accretion expense												0.8
Interest expense												(9.4)
Income (loss) from continuing operations before income tax expense												$ 3.2
Alon USA Energy, Inc. | Tax Effect Adjustment
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
U.S. income tax statutory blended rate (percentage)												37.00%
Alon USA Energy, Inc.
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Equity interest issued per acquiree share	0.504