Revenues - Contract Balances, Unearned Revenue and Remaining Performance Obligation (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Oct. 31, 2020	Oct. 31, 2019	Oct. 31, 2020	Oct. 31, 2019	Jan. 31, 2020
Revenue from Contract with Customer [Abstract]
Customer contract assets	$ 574		$ 574		$ 449
Unearned Revenue [Roll Forward]
Unearned revenue, beginning of period	8,711	$ 7,142	10,662	$ 8,564
Billings and other	4,561	3,886	12,498	9,996
Contribution from contract asset	66	61	125	112
Unearned revenue from business combinations	4	282	73	433
Unearned revenue, end of period	7,923	6,858	7,923	6,858
Remaining Performance Obligation
Current	15,300		15,300		15,000
Noncurrent	15,000		15,000		15,800
Total	30,300		30,300		$ 30,800
Revenue recognized ratably over time
Unearned Revenue [Roll Forward]
Revenue recognized	(4,911)	(4,047)	(14,021)	(11,270)
Revenue recognized over time as delivered
Unearned Revenue [Roll Forward]
Revenue recognized	(192)	(184)	(573)	(530)
Revenue recognized at a point in time
Unearned Revenue [Roll Forward]
Revenue recognized	$ (316)	$ (282)	$ (841)	$ (447)