Stock Repurchase Program - Additional Information (Detail) (USD $)	3 Months Ended		6 Months Ended
	Apr. 30, 2015	Jan. 31, 2015	Apr. 30, 2015	Dec. 31, 2014	Dec. 03, 2013
Stock Repurchase Program [Abstract]
Stock repurchase program authorized amount	$ 500,000,000.0		$ 500,000,000.0		$ 500,000,000.0
Remaining amount available for further repurchases	200,300,000.0		200,300,000.0
Accelerated share repurchase amount				180,000,000.0
Prepayment amount		180,000,000.0
Value of initial share delivery		144,000,000
Average price paid (in dollars per share)		$ 43.77
Remaining repurchase amount	$ 36,000,000		$ 36,000,000
Settlement period for remaining balance	6 months