Segment Information (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Segment Reporting Information [Line Items]
Net Sales	$ 3,266.1	$ 2,864.3	$ 9,024.4	$ 8,055.3
Number of Reportable Segments	2
Number of operating segments which do not meet reportable unit quantitative threshold	2
Income (loss) from operations	184.7	92.9	508.7	366.6
Depreciation and amortization expense	(51.8)	(52.0)	(155.9)	(156.3)
Corporate Segment: Private Sector Business [Member]
Segment Reporting Information [Line Items]
Net Sales	1,622.7	1,465.8	4,784.5	4,407.1
Income (loss) from operations	103.2	63.2	323.9	260.5
Depreciation and amortization expense	(24.1)	(24.3)	(72.3)	(73.1)
Public [Member]
Segment Reporting Information [Line Items]
Net Sales	1,468.8	1,244.6	3,710.3	3,174.0
Income (loss) from operations	101.3	71.1	244.1	185.8
Depreciation and amortization expense	(10.9)	(11.0)	(32.8)	(33.1)
Other [Member]
Segment Reporting Information [Line Items]
Net Sales	174.6	153.9	529.6	474.2
Income (loss) from operations	8.5	3.7	22.7	18.6
Depreciation and amortization expense	(2.2)	(2.1)	(6.5)	(6.6)
Headquarters [Member]
Segment Reporting Information [Line Items]
Net Sales	0	0	0	0
Income (loss) from operations	(28.3)	(45.1)	(82.0)	(98.3)
Depreciation and amortization expense	$ (14.6)	$ (14.6)	$ (44.3)	$ (43.5)