Shareholders' Equity - Common Share Repurchases and Issuance Activity (Detail) (USD $)	9 Months Ended
	Oct. 31, 2012
Stockholders Equity [Line Items]
Treasury stock held at January 31, 2012	18,166,761
Shares of common stock repurchased under share repurchase programs and other shares acquired	3,823,217
Shares of treasury stock reissued	(511,458)
Treasury stock held at October 31, 2012	21,478,520
Treasury stock held at January 31, 2012, Weighted-average price per share	$ 40.71
Shares of common stock repurchased under share repurchase program, Weighted-average price per share	$ 49.40
Treasury stock held at October 31, 2012, Weighted-average price per share	$ 42.25