Stockholders' Equity - Schedule of Changes in Stockholders' Equity (Details) - USD ($) $ / shares in Units, $ in Millions				1 Months Ended	3 Months Ended		6 Months Ended
	Feb. 26, 2018	Jan. 23, 2018	May 08, 2017	Dec. 31, 2017	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at December 31, 2017							$ 1,964.2
Net income					$ 86.7	$ (32.2)	66.7	$ (16.9)
Foreign currency translation (loss) gain					(0.2)	0.1	(0.6)	0.1
Other comprehensive income from equity method investments, net of income tax expense of a nominal amount					0.0	0.0	0.0	0.1
Other comprehensive income related to postretirement benefit plans					0.0	$ 0.0	0.1	$ 0.0
Common stock dividends ($0.45 per share)							(37.8)
Distributions to non-controlling interests							(14.1)
Equity-based compensation expense							10.4
Issuance of stock for non-controlling interest repurchase, net of tax							13.5
Noncontrolling Interest, Decrease from Deconsolidation							(18.7)
Cumulative effect of adopting accounting principle regarding income tax effect of intra-equity transfers					(29.9)		(29.9)
Repurchase of common stock		$ (75.3)		$ (25.0)	(20.0)		(115.3)
Taxes due to the net settlement of equity-based compensation							(8.8)
Balance at June 30, 2018				1,964.2	$ 1,779.3		1,779.3
Income tax benefit (expense) on unrealized gain on cash flow hedges							$ 13.3
Common stock dividends (in dollars per share)	$ 0.20		$ 0.25		$ 0.25	$ 0.15	$ 0.45	$ 0.30
Commodity contracts
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Other comprehensive (loss) income related to derivatives					$ (52.0)	$ 18.1	$ (49.9)	$ 19.3
Income tax benefit (expense) on unrealized gain on cash flow hedges					13.9	(9.8)	13.3	(10.4)
Ineffectiveness gain					0.7	$ 0.2	0.7	$ 0.4
Delek Stockholders' Equity
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at December 31, 2017							1,650.6
Net income							44.2
Foreign currency translation (loss) gain							(0.6)
Other comprehensive income related to postretirement benefit plans							0.1
Common stock dividends ($0.45 per share)							(37.8)
Distributions to non-controlling interests							0.0
Equity-based compensation expense							10.2
Issuance of stock for non-controlling interest repurchase, net of tax							140.5
Noncontrolling Interest, Decrease from Deconsolidation							0.0
Cumulative effect of adopting accounting principle regarding income tax effect of intra-equity transfers					(29.9)		(29.9)
Repurchase of common stock							(115.3)
Taxes due to the net settlement of equity-based compensation							(8.8)
Balance at June 30, 2018				1,650.6	1,602.8		1,602.8
Delek Stockholders' Equity | Commodity contracts
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Other comprehensive (loss) income related to derivatives							(49.9)
Delek Stockholders' Equity | Interest rate derivatives
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Other comprehensive (loss) income related to derivatives							(0.5)
Non-Controlling Interest in Subsidiaries
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at December 31, 2017							313.6
Net income							22.5
Foreign currency translation (loss) gain							0.0
Other comprehensive income related to postretirement benefit plans							0.0
Common stock dividends ($0.45 per share)							0.0
Distributions to non-controlling interests							(14.1)
Equity-based compensation expense							0.2
Issuance of stock for non-controlling interest repurchase, net of tax							(127.0)
Noncontrolling Interest, Decrease from Deconsolidation							(18.7)
Cumulative effect of adopting accounting principle regarding income tax effect of intra-equity transfers					0.0		0.0
Repurchase of common stock							0.0
Taxes due to the net settlement of equity-based compensation							0.0
Balance at June 30, 2018				$ 313.6	$ 176.5		176.5
Non-Controlling Interest in Subsidiaries | Commodity contracts
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Other comprehensive (loss) income related to derivatives							0.0
Non-Controlling Interest in Subsidiaries | Interest rate derivatives
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Other comprehensive (loss) income related to derivatives							$ 0.0