Share Repurchases (Schedule Of Company's Share Repurchases) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	6 Months Ended
	Jul. 31, 2018	Jul. 31, 2017
Equity, Class of Treasury Stock [Line Items]
Total number of shares repurchased	20.8	60.6
Average price paid per share	$ 88.81	$ 73.38
Total amount paid for share repurchases	$ 1,844	$ 4,447