Condensed Consolidated Statements of Operations - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Income Statement [Abstract]
Net sales	$ 3,805.9	$ 3,504.2
Cost of goods sold	3,606.1	3,330.2
Gross profit	199.8	174.0
Warehousing and distribution expenses	132.3	114.7
Selling, general and administrative expenses	63.4	55.3
Amortization of intangible assets	2.5	1.8
Total operating expenses	198.2	171.8
Income from operations	1.6	2.2
Interest expense	(3.9)	(2.0)
Interest income	0.1	0.1
Foreign currency transaction gains, net	0.4	0.6
(Loss) income before income taxes	(1.8)	0.9
Benefit from income taxes (Note 7)	0.5	1.2
Net (loss) income	$ (1.3)	$ 2.1
Basic and diluted net (loss) income per common share (in dollars per share) (Note 9)	$ (0.03)	$ 0.05
Basic weighted-average shares (in shares) (Note 9)	46.2	46.3
Diluted weighted-average shares (in shares) (Note 9)	46.2	46.4
Dividends declared per common share (in dollars per share) (Note 11)	$ 0.10	$ 0.09
Dividends paid per common share (in dollars per share) (Note 11)	$ 0.10	$ 0.09