Retirement-Related Benefits (Schedule of Contribution Expense Related to Defined Contribution Plans) (Details) - USD ($) $ in Millions	12 Months Ended
	Jan. 31, 2021	Jan. 31, 2020	Jan. 31, 2019
Contribution expense from retirement plans [Line Items]
Total contribution expense for defined contribution plans	$ 1,490	$ 1,361	$ 1,291
UNITED STATES
Contribution expense from retirement plans [Line Items]
Total contribution expense for defined contribution plans	1,290	1,184	1,165
Foreign Plan [Member]
Contribution expense from retirement plans [Line Items]
Total contribution expense for defined contribution plans	$ 200	$ 177	$ 126