Condensed Consolidated Statements of Operations (Parenthetical) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jul. 31, 2019	Jul. 31, 2018	Jul. 31, 2019	Jul. 31, 2018
Stock-based expenses	$ 388	$ 351	$ 731	$ 603
Cost of revenues
Amortization of purchased intangibles from business combinations	62	52	123	91
Stock-based expenses	46	43	89	77
Research and development
Stock-based expenses	98	81	179	147
Marketing and sales
Amortization of purchased intangibles from business combinations	65	67	133	97
Stock-based expenses	199	174	376	294
General and administrative
Stock-based expenses	$ 45	$ 53	$ 87	$ 85