Condensed Consolidated Statements of Operations - USD ($) shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Income Statement [Abstract]
Net sales	$ 4,263.9	$ 4,339.0	$ 8,203.2	$ 8,093.1
Cost of goods sold	4,050.8	4,100.1	7,771.7	7,646.0
Gross profit	213.1	238.9	431.5	447.1
Warehousing and distribution expenses	125.5	143.2	267.9	277.4
Selling, general and administrative expenses	59.8	64.6	123.7	130.5
Amortization of intangible assets	2.4	2.7	4.7	5.4
Total operating expenses	187.7	210.5	396.3	413.3
Income from operations	25.4	28.4	35.2	33.8
Interest expense, net	(2.8)	(3.2)	(6.3)	(6.6)
Foreign currency transaction losses, net	0.0	(1.0)	(0.2)	(1.2)
Income before income taxes	22.6	24.2	28.7	26.0
Provision for income taxes	(5.7)	(6.5)	(7.5)	(7.0)
Net income	$ 16.9	$ 17.7	$ 21.2	$ 19.0
Basic earnings per share (in dollars per share) (Note 6)	$ 0.38	$ 0.39	$ 0.47	$ 0.41
Diluted earnings per share (in dollars per share) (Note 6)	$ 0.38	$ 0.38	$ 0.47	$ 0.41
Basic weighted-average shares (in shares) (Note 6)	45.1	45.9	45.2	45.9
Diluted weighted-average shares (in shares) (Note 6)	45.3	46.1	45.4	46.1