Condensed Consolidated Statements of Operations (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Income Statement [Abstract]
Net sales	$ 2,452.3	$ 2,300.9
Cost of goods sold	2,315.0	2,176.5
Gross profit	137.3	124.4
Warehousing and distribution expenses	79.5	75.3
Selling, general and administrative expenses	47.3	43.9
Amortization of intangible assets	0.6	0.6
Total operating expenses	127.4	119.8
Income from operations	9.9	4.6
Interest expense	(0.6)	(0.7)
Interest income	0.2	0.1
Foreign currency transaction losses, net	(0.4)	0
Income before income taxes	9.1	4.0
Provision for income taxes	(3.6)	(1.6)
Net income	$ 5.5	$ 2.4
Basic net income per common share (in dollars per share)	$ 0.24	$ 0.11
Diluted net income per common share (in dollars per share)	$ 0.24	$ 0.10
Basic weighted-average shares	23.2	23.0
Diluted weighted-average shares	23.3	23.2
Dividends declared per common share (in dollars per share)	$ 0.13	$ 0.11
Dividends paid per common share (in dollars per share)	$ 0.13	$ 0.11