Revenues - Contract Balances and Unearned Revenue (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jul. 31, 2021	Jul. 31, 2020	Jul. 31, 2021	Jul. 31, 2020	Jan. 31, 2021
Revenue from Contract with Customer [Abstract]
Customer contract assets	$ 647		$ 647		$ 477
Unearned Revenue [Roll Forward]
Unearned revenue, beginning of period	11,158	$ 9,112	12,607	$ 10,662
Billings and other	5,771	4,632	10,209	7,937
Contribution from contract asset	96	54	170	59
Unearned revenue from business combinations	382	64	384	69
Unearned revenue, end of period	11,067	8,711	11,067	8,711
Revenue recognized over time
Unearned Revenue [Roll Forward]
Revenue recognized	(5,948)	(4,847)	(11,559)	(9,491)
Revenue recognized at a point in time
Unearned Revenue [Roll Forward]
Revenue recognized	$ (392)	$ (304)	$ (744)	$ (525)