Stock Repurchase Program - Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified	1 Months Ended	12 Months Ended			3 Months Ended
	May 25, 2011	Oct. 31, 2012	Oct. 31, 2011	Oct. 31, 2010	Apr. 30, 2012 Accelerated Share Repurchase Agreement	Jan. 31, 2012 Accelerated Share Repurchase Agreement	Oct. 31, 2011 Accelerated Share Repurchase Agreement	Jan. 06, 2012 Accelerated Share Repurchase Agreement	Sep. 30, 2011 Accelerated Share Repurchase Agreement
Stock Repurchase Program [Line Items]
Stock repurchase program authorized amount	$ 500.0	$ 500.0
Stock repurchase program remaining authorized repurchase amount		272.4
Accelerated share repurchase agreement amount								40.0	75.0
Stock repurchase program prepayment									75.0
Initial number of shares received from accelerated share repurchase agreements							1,710,376
Initial share value							41.7
Remaining balance of value or shares to be settled							$ 33.3
Number of shares to settle equity forward contract					1,368,616	1,105,457
Average purchase price per share		$ 29.64	$ 26.53	$ 22.43	$ 29.23	$ 26.64