Segment Information (Details) $ in Millions	3 Months Ended
	Mar. 31, 2017 USD ($) segment	Mar. 31, 2016 USD ($)
Segment Reporting Information [Line Items]
Number of Reportable Segments | segment	3
Number of operating segments which do not meet reportable unit quantitative threshold | segment	2
Net Sales	$ 3,324.7	$ 3,116.7
Income (loss) from operations	169.8	161.0
Depreciation and amortization expense	(64.2)	(64.0)
Corporate [Member]
Segment Reporting Information [Line Items]
Net Sales	1,476.3	1,414.9
Income (loss) from operations	111.4	101.5
Depreciation and amortization expense	(20.8)	(20.8)
Small Business Segment Private Sector Business [Domain]
Segment Reporting Information [Line Items]
Net Sales	298.7	277.4
Income (loss) from operations	16.6	16.7
Depreciation and amortization expense	5.1	5.1
Public [Member]
Segment Reporting Information [Line Items]
Net Sales	1,176.5	1,069.4
Income (loss) from operations	60.7	58.5
Depreciation and amortization expense	(11.2)	(11.2)
Other [Member]
Segment Reporting Information [Line Items]
Net Sales	373.2	355.0
Income (loss) from operations	12.6	8.1
Depreciation and amortization expense	(7.2)	(8.7)
Headquarters [Member]
Segment Reporting Information [Line Items]
Net Sales	0.0	0.0
Income (loss) from operations	(31.5)	(23.8)
Depreciation and amortization expense	$ (19.9)	$ (18.2)