Segment and Geographic Information - Geographic Reporting Segments Table (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2013		Jun. 30, 2012		Jun. 30, 2013		Jun. 30, 2012
Net sales: [Abstract]
Net sales	$ 2,509.9		$ 2,287.3		$ 4,655.6		$ 4,388.0
Income (loss) before income taxes: [Abstract]
Income (loss) before income taxes	19.8		17.1		23.9		22.9
Interest expense: [Abstract]
Interest expense	0.8		0.6		1.5		1.2
Depreciation and amortization: [Abstract]
Depreciation and amortization	6.8		6.4		13.4		12.7
Reportable Geographical Components [Member] | United States [Member]
Net sales: [Abstract]
Net sales	2,218.7		1,984.4		4,124.3		3,802.9
Income (loss) before income taxes: [Abstract]
Income (loss) before income taxes	18.2		15.5		21.9		19.0
Interest expense: [Abstract]
Interest expense	7.5		7.0		14.4		13.4
Depreciation and amortization: [Abstract]
Depreciation and amortization	4.9		4.4		9.8		8.7
Reportable Geographical Components [Member] | Canada [Member]
Net sales: [Abstract]
Net sales	281.3		295.2		513.5		569.8
Income (loss) before income taxes: [Abstract]
Income (loss) before income taxes	0.2		0.7		(0.1)		0.9
Interest expense: [Abstract]
Interest expense	0.1		0.2		0.4		0.4
Depreciation and amortization: [Abstract]
Depreciation and amortization	0.7		0.8		1.4		1.5
Corporate [Member]
Net sales: [Abstract]
Net sales	9.9	[1]	7.7	[1]	17.8	[1]	15.3	[1]
Income (loss) before income taxes: [Abstract]
Income (loss) before income taxes	1.4	[1]	0.9	[1]	2.1	[1]	3.0	[1]
Interest expense: [Abstract]
Interest expense	(6.8)	[1]	(6.6)	[1]	(13.3)	[1]	(12.6)	[1]
Depreciation and amortization: [Abstract]
Depreciation and amortization	$ 1.2	[1]	$ 1.2	[1]	$ 2.2	[1]	$ 2.5	[1]

[1] Corporate consists primarily of net expenses and other income that is not allocated to the U.S. and Canada, intercompany eliminations for interest and allocations of overhead, and LIFO income or expense.