Segment Information - Schedule of Segment Information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Segment Reporting Information [Line Items]
Net sales	$ 4,389.2	$ 3,957.9
Income (loss) from operations	245.8	228.9
Depreciation and amortization expense	(91.4)	(64.3)
Operating Segments | Corporate
Segment Reporting Information [Line Items]
Net sales	1,911.0	1,736.2
Income (loss) from operations	127.4	134.7
Depreciation and amortization expense	(22.3)	(21.5)
Operating Segments | Small Business
Segment Reporting Information [Line Items]
Net sales	391.5	355.6
Income (loss) from operations	27.3	24.4
Depreciation and amortization expense	(5.8)	(5.6)
Operating Segments | Public
Segment Reporting Information [Line Items]
Net sales	1,525.3	1,330.7
Income (loss) from operations	112.4	76.1
Depreciation and amortization expense	(37.7)	(12.7)
Operating Segments | Other
Segment Reporting Information [Line Items]
Net sales	561.4	535.4
Income (loss) from operations	14.7	25.6
Depreciation and amortization expense	(8.0)	(7.4)
Headquarters
Segment Reporting Information [Line Items]
Net sales	0.0	0.0
Income (loss) from operations	(36.0)	(31.9)
Depreciation and amortization expense	$ (17.6)	$ (17.1)