Derivative Financial Instruments - Outstanding Derivative Contracts Entered into Hedge Forecasted Purchases and Future Cash Receipts (Detail) (USD $) In Thousands, unless otherwise specified	Jan. 31, 2013
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Notional Amount	$ 187,913
Fair Value	2,949
Inventory Commodity [Member] | United States Dollar [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Notional Amount	175,930
Fair Value	2,477
Accounts receivable Commodity [Member] | British pounds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Notional Amount	11,983
Fair Value	$ 472
Minimum [Member] | Inventory Commodity [Member] | United States Dollar [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Maturity	2013-02
Minimum [Member] | Accounts receivable Commodity [Member] | British pounds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Maturity	2013-02
Maximum [Member] | Inventory Commodity [Member] | United States Dollar [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Maturity	2013-10
Maximum [Member] | Accounts receivable Commodity [Member] | British pounds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Maturity	2013-10