Share Repurchases (Schedule Of Company's Share Repurchases) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Apr. 30, 2017	Apr. 30, 2016
Equity, Class of Treasury Stock [Line Items]
Total number of shares repurchased	31.1	40.7
Average price paid per share	$ 70.25	$ 67.23
Total amount paid for share repurchases	$ 2,185	$ 2,735