Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jul. 31, 2019	Jul. 31, 2018	Jul. 31, 2019	Jul. 31, 2018
Statement of Comprehensive Income [Abstract]
Net income	$ 91	$ 299	$ 483	$ 643
Other comprehensive loss, net of reclassification adjustments:
Foreign currency translation and other losses	(17)	(17)	(30)	(27)
Unrealized gains (losses) on marketable securities and privately held debt securities	6	0	14	(4)
Other comprehensive loss, before tax	(11)	(17)	(16)	(31)
Tax effect	(1)	0	(3)	0
Other comprehensive loss, net	(12)	(17)	(19)	(31)
Comprehensive income	$ 79	$ 282	$ 464	$ 612