INVENTORIES (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020	Dec. 31, 2019
Inventory [Line Items]
Crude oil and feedstocks	$ 1,156.4		$ 1,156.4			$ 1,018.9
Refined products and blendstocks	1,341.8		1,341.8			1,200.2
Warehouse stock and other	138.0		138.0			136.7
Inventory, Gross	2,636.2		2,636.2			2,355.8
Lower of cost or market adjustment	0.0		0.0			(669.6)
Total inventories	2,636.2		2,636.2			1,686.2
Income (loss) from operations	147.5	$ 620.8	205.2	$ (746.0)
Titled Inventory [Member]
Inventory [Line Items]
Crude oil and feedstocks	1,156.4		1,156.4			1,018.9
Refined products and blendstocks	1,041.2		1,041.2			933.7
Warehouse stock and other	138.0		138.0			136.7
Inventory, Gross	2,335.6		2,335.6			2,089.3
Lower of cost or market adjustment	0.0		0.0			(572.4)
Total inventories	2,335.6		2,335.6			1,516.9
Inventory Supply and Offtake Arrangements [Member]
Inventory [Line Items]
Crude oil and feedstocks	0.0		0.0			0.0
Refined products and blendstocks	300.6		300.6			266.5
Warehouse stock and other	0.0		0.0			0.0
Inventory, Gross	300.6		300.6			266.5
Lower of cost or market adjustment	0.0		0.0			(97.2)
Total inventories	300.6		300.6			169.3
Scenario, Adjustment [Member]
Inventory [Line Items]
Lower of cost or market adjustment	0.0	(1,103.0)	0.0	(1,103.0)	$ (264.0)	$ (669.6)	$ (1,687.2)	$ (401.6)
Income (loss) from operations	$ 264.0	$ 584.2	$ 669.6	$ 701.4