Condensed Consolidated Statements of Operations (Unaudited) - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Income Statement [Abstract]
Net sales	$ 3,011.3	$ 2,452.3
Cost of goods sold	2,860.2	2,315.0
Gross profit	151.1	137.3
Warehousing and distribution expenses	91.6	79.5
Selling, general and administrative expenses	49.4	47.3
Amortization of intangible assets	0.9	0.6
Total operating expenses	141.9	127.4
Income from operations	9.2	9.9
Interest expense	(0.8)	(0.6)
Interest income	0.1	0.2
Foreign currency transaction gains (losses), net	0.7	(0.4)
Income before income taxes	9.2	9.1
Provision for income taxes	(3.5)	(3.6)
Net income	$ 5.7	$ 5.5
Basic net income per common share (in dollars per share)	$ 0.24	$ 0.24
Basic weighted-average shares	23.2	23.2
Diluted weighted-average shares	23.3	23.3
Dividends declared per common share (in dollars per share)	$ 0.16	$ 0.13