Segment Information - Products and Services (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Net Sales from External Customer [Line Items]
Net sales	$ 4,536.9	$ 4,907.7	$ 4,629.9	$ 3,957.9	$ 4,074.8	$ 4,373.2	$ 4,186.1	$ 3,606.4	$ 18,032.4	$ 16,240.5	$ 14,832.9
Percentage of Total Net Sales									100.00%	100.00%	100.00%
Total Hardware
Net Sales from External Customer [Line Items]
Net sales									$ 14,363.2	$ 13,099.1	$ 11,971.8
Percentage of Total Net Sales									79.80%	80.60%	80.60%
Notebooks/Mobile Devices
Net Sales from External Customer [Line Items]
Net sales									$ 4,631.7	$ 4,062.2	$ 3,491.8
Percentage of Total Net Sales									25.70%	25.00%	23.50%
Netcomm Products
Net Sales from External Customer [Line Items]
Net sales									$ 2,193.4	$ 2,119.1	$ 2,021.6
Percentage of Total Net Sales									12.20%	13.00%	13.60%
Desktops
Net Sales from External Customer [Line Items]
Net sales									$ 1,598.2	$ 1,322.2	$ 1,196.0
Percentage of Total Net Sales									8.90%	8.10%	8.10%
Video
Net Sales from External Customer [Line Items]
Net sales									$ 1,272.7	$ 1,184.3	$ 1,070.0
Percentage of Total Net Sales									7.10%	7.30%	7.20%
Enterprise and Data Storage (Including Drives)
Net Sales from External Customer [Line Items]
Net sales									$ 1,146.0	$ 1,102.5	$ 1,070.2
Percentage of Total Net Sales									6.40%	6.80%	7.20%
Other Hardware
Net Sales from External Customer [Line Items]
Net sales									$ 3,521.2	$ 3,308.8	$ 3,122.2
Percentage of Total Net Sales									19.50%	20.40%	21.00%
Software
Net Sales from External Customer [Line Items]
Net sales									$ 2,637.2	$ 2,331.9	$ 2,145.4
Percentage of Total Net Sales									14.60%	14.40%	14.50%
Services
Net Sales from External Customer [Line Items]
Net sales									$ 907.6	$ 695.8	$ 602.8
Percentage of Total Net Sales									5.00%	4.30%	4.10%
Other
Net Sales from External Customer [Line Items]
Net sales									$ 124.4	$ 113.7	$ 112.9
Percentage of Total Net Sales									0.60%	0.70%	0.80%