Selected Quarterly Financial Data (Unaudited) - Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Income (loss) from continuing operations	$ 127.6	$ 185.8	$ 87.5	$ (17.3)	$ 226.9	$ 118.5	$ (32.2)	$ 15.3	$ 383.6	$ 328.5	$ (219.7)
Less: Income from continuing operations attributed to non-controlling interest	5.8				14.0
Income (loss) from continuing operations attributable to Delek (numerator for basic EPS - continuing operations attributable to Delek)	121.8				212.9				356.9	294.7	(240.0)
Interest on convertible debt, net of tax	0.0				0.7				2.6	0.0	0.0
Numerator for diluted EPS - continuing operations attributable to Delek	121.8				213.6
Income (loss) from discontinued operations	$ (0.2)				$ (1.8)				$ (8.7)	$ (5.9)	$ 86.3
Weighted average common shares outstanding (in shares)	81,321,240				81,338,755				82,797,110	71,566,225	61,921,787
Dilutive effect of convertible debt (in shares)	0				526,464				1,525,846	0	0
Dilutive effect of warrants (in shares)	260,838				0				967,352	0	0
Dilutive effect of stock-based awards (in shares)	946,261				779,841				1,478,093	736,858	0
Weighted average common shares outstanding, assuming dilution (in shares)	82,528,339				82,645,060				86,768,401	72,303,083	61,921,787
Income (loss) from continuing operations (USD per share)	$ 1.50	$ 2.15	$ 0.95	$ (0.29)	$ 2.62	$ 1.30	$ (0.61)	$ 0.18	$ 4.31	$ 4.12	$ (3.88)
(Loss) income from discontinued operations (USD per share)	0				(0.02)				(0.20)	(0.08)	1.39
Total basic income (loss) per share (USD per share)	1.50				2.60				4.11	4.04	(2.49)
Income from continuing operations (USD per share)	1.48	$ 2.02	$ 0.90	$ (0.29)	2.58	$ 1.29	$ (0.61)	$ 0.18	4.14	4.08	(3.88)
(Loss) income from discontinued operations (USD per share)	0				(0.02)				(0.19)	(0.08)	1.39
Total diluted income (loss) per share (USD per share)	$ 1.48				$ 2.56				$ 3.95	$ 4.00	$ (2.49)
Total antidilutive stock-based compensation
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	1,749,569				3,660,354				1,462,112	0	2,573,221
Antidilutive stock-based compensation
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	1,749,569				3,660,354				1,462,112		2,297,127
Antidilutive due to loss
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	0				0				0		276,094
Antidilutive convertible debt instruments
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	0				5,623,304				0	2,811,652	0
Antidilutive warrants
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	0				5,612,581				0	2,806,291	0