Condensed Consolidated Statements of Operations - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Income Statement [Abstract]
Net sales	$ 3,932.2	$ 3,939.3
Cost of goods sold	3,714.8	3,720.9
Gross profit	217.4	218.4
Warehousing and distribution expenses	137.3	142.4
Selling, general and administrative expenses	63.4	63.9
Amortization of intangible assets	2.7	2.3
Total operating expenses	203.4	208.6
Income from operations	14.0	9.8
Interest expense, net	(3.1)	(3.5)
Foreign currency transaction gains (losses), net	0.2	(0.2)
Income before income taxes	11.1	6.1
Provision for income taxes	(2.6)	(1.8)
Net income	$ 8.5	$ 4.3
Basic earnings per share (in dollars per share) (Note 6)	$ 0.19	$ 0.09
Diluted earnings per share (in dollars per share) (Note 6)	$ 0.19	$ 0.09
Basic weighted-average shares (in shares) (Note 6)	45.2	45.3
Diluted weighted-average shares (in shares) (Note 6)	45.4	45.4