Credit and Term Loan Facilities - Additional Information (Detail) (USD $)	3 Months Ended	9 Months Ended
	Jul. 31, 2012	Jul. 31, 2012	Feb. 17, 2012	Oct. 31, 2011
Debt Instrument [Line Items]
Senior unsecured revolving credit facility entered date		Feb. 17, 2012
Senior unsecured revolving credit facility maximum borrowing capacity			$ 350,000,000
Senior unsecured revolving credit facility financial covenants		The Credit Agreement contains financial covenants requiring the Company to operate within a maximum leverage ratio and maintain specified levels of cash, as well as other non-financial covenants.
Senior unsecured Term Loan facility, face amount			150,000,000
Credit Agreement termination date		Oct. 14, 2016
Senior unsecured term loan facility additional borrowings		150,000,000
Outstanding borrowing under revolving credit facility	0	0		0
Senior unsecured Term Loan facility	142,500,000	142,500,000
Repayment on Term Loan	7,500,000	7,500,000
Principal payment on revolving credit facility	100,000,000	100,000,000
Senior unsecured term loan facility long term	$ 112,500,000	$ 112,500,000
Minimum
Debt Instrument [Line Items]
Commitment fees percentage		0.15%
Maximum
Debt Instrument [Line Items]
Commitment fees percentage		0.30%
Original Credit Agreement
Debt Instrument [Line Items]
Senior unsecured revolving credit facility entered date		Oct. 14, 2011
Revolver
Debt Instrument [Line Items]
Term loan interest rate	0.975%	0.975%
Term Loan
Debt Instrument [Line Items]
Term loan interest rate	1.125%	1.125%