Taxes (Schedule of Income Tax Provision) (Details) - USD ($) $ in Millions	12 Months Ended
	Jan. 31, 2019	Jan. 31, 2018	Jan. 31, 2017
Taxes [Abstract]
U.S. federal	$ 2,763	$ 2,998	$ 3,454
U.S. state and local	493	405	495
International	1,495	1,377	1,510
Total current tax provision	4,751	4,780	5,459
U.S. federal	(361)	(22)	1,054
U.S. state and local	(16)	(12)	51
International	(93)	(146)	(360)
Total deferred tax expense (benefit)	(470)	(180)	745
Total provision for income taxes	$ 4,281	$ 4,600	$ 6,204