Selected Quarterly Financial Results (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended																12 Months Ended
	Dec. 31, 2013		Sep. 30, 2013		Jun. 30, 2013		Mar. 31, 2013		Dec. 31, 2012		Sep. 30, 2012		Jun. 30, 2012		Mar. 31, 2012		Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
IPO Related Expenses			$ 74.1
Net Sales	2,713.3		2,864.3		2,779.3		2,411.7		2,601.0		2,623.3		2,584.7		2,319.2		10,768.6	10,128.2	9,602.4
Gross Profit	448.3		458.4		451.6		402.0		425.4		432.7		426.9		384.6		1,760.3	1,669.6	1,583.5
Income (loss) from operations	142.0		92.9	[1]	153.6		120.1		130.9		139.7		136.4		103.6		508.6	510.6	470.7
Net income (loss)	60.0		(2.2)	[1]	46.7		28.3		33.3		38.0		36.8		10.9		132.8	119.0	17.1
Basic	$ 0.35	[2]	$ (0.01)	[1],[2]	$ 0.32	[2]	$ 0.19	[2]	$ 0.23	[2]	$ 0.26	[2]	$ 0.25	[2]	$ 0.08	[2]	$ 0.85	$ 0.82	$ 0.12
Diluted	$ 0.35	[2]	$ (0.01)	[1],[2]	$ 0.32	[2]	$ 0.19	[2]	$ 0.23	[2]	$ 0.26	[2]	$ 0.25	[2]	$ 0.07	[2]	$ 0.84	$ 0.82	$ 0.12
Corporate [Member]
Net Sales	1,553.0		1,465.8		1,537.4		1,403.9		1,442.8		1,312.8		1,394.4		1,362.8		5,960.1	5,512.8	5,334.4
Income (loss) from operations																	363.3	349.0	331.6
Corporate [Member] | Medium/Large [Member]
Net Sales	1,281.6		1,203.4		1,271.4		1,146.2		1,178.5		1,055.7		1,124.7		1,089.6
Corporate [Member] | Small Business [Member]
Net Sales	271.4		262.4		266.0		257.7		264.3		257.1		269.7		273.2
Public [Member]
Net Sales	990.5		1,244.6		1,082.6		846.8		1,001.3		1,163.7		1,040.4		817.6		4,164.5	4,023.0	3,757.2
Income (loss) from operations																	246.5	246.7	233.3
Public [Member] | Government [Member]
Net Sales	327.3		375.3		295.7		252.3		404.9		408.6		318.0		262.6
Public [Member] | Education [Member]
Net Sales	282.8		513.4		420.6		232.2		226.4		394.7		349.5		221.7
Public [Member] | Healthcare [Member]
Net Sales	380.4		355.9		366.3		362.3		370.0		360.4		372.9		333.3
Other [Member]
Net Sales	169.8		153.9		159.3		161.0		156.9		146.8		149.9		138.8		644.0	592.4	510.8
Income (loss) from operations																	$ 27.2	$ 18.6	$ 17.5

[1] The third quarter of 2013 included pre-tax IPO-related charges of $74.1 million. See Note 9 for additional discussion of the IPO.

[2] Basic and diluted net income (loss) per share are computed independently for each of the quarters presented. Therefore, the sum of quarterly basic and diluted per share information may not equal annual basic and diluted net income (loss) per share.