Business Combinations (Pro Forma Information) (Details) - USD ($) $ in Millions	6 Months Ended	9 Months Ended	12 Months Ended
	Jan. 31, 2020	Jan. 31, 2019	Jan. 31, 2020	Jan. 31, 2019
Tableau Software, Inc.
Business Acquisition [Line Items]
Total revenues	$ 689
Pretax loss	$ (503)
Total revenues			$ 17,599	$ 14,256
Pretax income (loss)			270	(82)
Net income (loss)			$ (292)	$ 297
MuleSoft
Business Acquisition [Line Items]
Total revenues		$ 431
Pretax loss		$ (286)