Common Stock Repurchase Program Additional Information (Details) - Jul. 31, 2015 - USD ($) $ / shares in Units, shares in Millions, $ in Millions	Total	Total
Common Stock
Equity, Class of Treasury Stock [Line Items]
Repurchased shares of its common stock on the open market, value	$ 48.0	$ 89.1
Retained Earnings
Equity, Class of Treasury Stock [Line Items]
Repurchased shares of its common stock on the open market, value	$ 64.3	$ 118.6
Common Stock Repurchase Program
Equity, Class of Treasury Stock [Line Items]
Common stock repurchased and retired (in shares)	2.1	3.7
Repurchased shares of its common stock on the open market, average repurchase price per share (in usd per share)	$ 52.87	$ 56.19
Common Stock shares remained available for repurchase under repurchase plans (in shares)	11.1	11.1