Intangible Assets Acquired Through Business Combinations and Goodwill (Intangible Assets Acquired From Business Combinations) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jul. 31, 2020	Jul. 31, 2019	Jul. 31, 2020	Jul. 31, 2019	Jan. 31, 2020
Finite-lived Intangible Assets [Roll Forward]
Intangible assets, gross, beginning balance			$ 6,922
Additions and retirements, net			507
Intangible assets, gross, ending balance	$ 7,429		7,429
Accumulated amortization, beginning balance			(2,198)
Expense and retirements, net			(555)
Accumulated amortization, ending balance	(2,753)		(2,753)
Intangible assets, net, beginning balance			4,724
Intangible assets, net, ending balance	4,676		$ 4,676
Weighted average remaining useful life			5 years 6 months
Amortization of intangible assets	284	$ 127	$ 555	$ 256
Customer contract assets	508		508		$ 449
Other assets
Finite-lived Intangible Assets [Roll Forward]
Customer contract assets	67		67		$ 93
Acquired developed technology
Finite-lived Intangible Assets [Roll Forward]
Intangible assets, gross, beginning balance			3,598
Additions and retirements, net			185
Intangible assets, gross, ending balance	3,783		3,783
Accumulated amortization, beginning balance			(1,249)
Expense and retirements, net			(325)
Accumulated amortization, ending balance	(1,574)		(1,574)
Intangible assets, net, beginning balance			2,349
Intangible assets, net, ending balance	2,209		$ 2,209
Weighted average remaining useful life			3 years 7 months 6 days
Customer relationships
Finite-lived Intangible Assets [Roll Forward]
Intangible assets, gross, beginning balance			$ 3,252
Additions and retirements, net			316
Intangible assets, gross, ending balance	3,568		3,568
Accumulated amortization, beginning balance			(888)
Expense and retirements, net			(218)
Accumulated amortization, ending balance	(1,106)		(1,106)
Intangible assets, net, beginning balance			2,364
Intangible assets, net, ending balance	2,462		$ 2,462
Weighted average remaining useful life			7 years 2 months 12 days
Other
Finite-lived Intangible Assets [Roll Forward]
Intangible assets, gross, beginning balance			$ 72
Additions and retirements, net			6
Intangible assets, gross, ending balance	78		78
Accumulated amortization, beginning balance			(61)
Expense and retirements, net			(12)
Accumulated amortization, ending balance	(73)		(73)
Intangible assets, net, beginning balance			11
Intangible assets, net, ending balance	$ 5		$ 5
Weighted average remaining useful life			3 years 8 months 12 days