Fair Value of Plan Assets Held by Asset Category (Detail) (USD $) In Thousands, unless otherwise specified	Aug. 31, 2012		Aug. 31, 2011		Aug. 31, 2010
Pension and Other Postretirement Benefits Disclosure [Line Items]
Fair value of plan assets	$ 133,430		$ 99,237		$ 85,571
Fair value of plan assets allocation	100.00%		100.00%
Level 1
Pension and Other Postretirement Benefits Disclosure [Line Items]
Fair value of plan assets	4,370		4,267
Level 2
Pension and Other Postretirement Benefits Disclosure [Line Items]
Fair value of plan assets	114,742		83,334
Level 3
Pension and Other Postretirement Benefits Disclosure [Line Items]
Fair value of plan assets	14,318		11,636
Cash and Cash Equivalents
Pension and Other Postretirement Benefits Disclosure [Line Items]
Fair value of plan assets	4,370		4,267
Fair value of plan assets allocation	3.00%		4.00%
Cash and Cash Equivalents | Level 1
Pension and Other Postretirement Benefits Disclosure [Line Items]
Fair value of plan assets	4,370		4,267
Equity Securities | Global Equity Securities
Pension and Other Postretirement Benefits Disclosure [Line Items]
Fair value of plan assets	22,649	[1]	11,933	[1]
Fair value of plan assets allocation	17.00%	[1]	12.00%	[1]
Equity Securities | U.K. Equity Securities
Pension and Other Postretirement Benefits Disclosure [Line Items]
Fair value of plan assets	18,544	[2]	12,130	[2]
Fair value of plan assets allocation	14.00%	[2]	12.00%	[2]
Equity Securities | Canadian Equity Securities
Pension and Other Postretirement Benefits Disclosure [Line Items]
Fair value of plan assets	8,247	[3]
Fair value of plan assets allocation	6.00%	[3]
Equity Securities | Level 2 | Global Equity Securities
Pension and Other Postretirement Benefits Disclosure [Line Items]
Fair value of plan assets	22,649	[1]	11,933	[1]
Equity Securities | Level 2 | U.K. Equity Securities
Pension and Other Postretirement Benefits Disclosure [Line Items]
Fair value of plan assets	18,544	[2]	12,130	[2]
Equity Securities | Level 2 | Canadian Equity Securities
Pension and Other Postretirement Benefits Disclosure [Line Items]
Fair value of plan assets	8,247	[3]
Debt Securities | U.K. Corporate Bonds
Pension and Other Postretirement Benefits Disclosure [Line Items]
Fair value of plan assets	42,983	[4]	27,146	[4]
Fair value of plan assets allocation	32.00%	[4]	28.00%	[4]
Debt Securities | U.K. Government Bonds
Pension and Other Postretirement Benefits Disclosure [Line Items]
Fair value of plan assets	13,562	[5]	32,125	[5]
Fair value of plan assets allocation	10.00%	[5]	32.00%	[5]
Debt Securities | Canadian Government Bonds
Pension and Other Postretirement Benefits Disclosure [Line Items]
Fair value of plan assets	8,757	[6]
Fair value of plan assets allocation	7.00%	[6]
Debt Securities | Level 2 | U.K. Corporate Bonds
Pension and Other Postretirement Benefits Disclosure [Line Items]
Fair value of plan assets	42,983	[4]	27,146	[4]
Debt Securities | Level 2 | U.K. Government Bonds
Pension and Other Postretirement Benefits Disclosure [Line Items]
Fair value of plan assets	13,562	[5]	32,125	[5]
Debt Securities | Level 2 | Canadian Government Bonds
Pension and Other Postretirement Benefits Disclosure [Line Items]
Fair value of plan assets	8,757	[6]
Insurance Contracts
Pension and Other Postretirement Benefits Disclosure [Line Items]
Fair value of plan assets	11,046	[7]	11,636	[7]
Fair value of plan assets allocation	8.00%	[7]	12.00%	[7]
Insurance Contracts | Level 3
Pension and Other Postretirement Benefits Disclosure [Line Items]
Fair value of plan assets	11,046	[7]	11,636	[7]
Commercial Real Estate
Pension and Other Postretirement Benefits Disclosure [Line Items]
Fair value of plan assets	1,987	[8]
Fair value of plan assets allocation	2.00%	[8]
Commercial Real Estate | Level 3
Pension and Other Postretirement Benefits Disclosure [Line Items]
Fair value of plan assets	1,987	[8]
Commercial Mortgages
Pension and Other Postretirement Benefits Disclosure [Line Items]
Fair value of plan assets	1,285	[9]
Fair value of plan assets allocation	1.00%	[9]
Commercial Mortgages | Level 3
Pension and Other Postretirement Benefits Disclosure [Line Items]
Fair value of plan assets	$ 1,285	[9]

[1] Global equity securities are categorized as Level 2 and include investments that aim to capture global equity market returns by tracking the Financial Times (London) Stock Exchange ("FTSE") AW-World (ex-UK) Index and other similar indexes in Canada.

[2] U.K. equity securities are categorized as Level 2 and include investments in a diversified portfolio that aims to capture the returns of the U.K. equity market. The portfolio tracks the FTSE All-Share Index and invests only in U.K. securities.

[3] Canadian equity securities are categorized as Level 2 and include investments in diversified portfolios that aim to capture the returns of Canadian small capitalization and dividend paying equities. The portfolios track the BMO Small Cap Index and the S&P/TSX Capped Equity Index and invest only in Canadian securities.

[4] U.K. corporate bonds are categorized as Level 2 and include U.K. corporate issued fixed income investments which are managed and tracked to the respective benchmark (AAA-AA-A Bonds-Over 15Y Index).

[5] U.K. government bonds are categorized as Level 2 and include U.K. government-issued fixed income investments which are managed and tracked to the respective benchmark (FTSE U.K. Over 15 Years Gilts Index and FTSE U.K. Over 5 Years Index-Linked).

[6] Canadian government bonds are categorized as Level 2 and include Canadian government-issued fixed income investments which are managed and tracked to the respective benchmark (DEX Universe Bond Index).

[7] The assets related to The Netherlands plan consist of an insurance contract that guarantees the payment of the funded pension entitlements, as well as provides a profit share to the Company. The profit share in this contract is not based on actual investments, but, instead on a notional investment portfolio that is expected to return a pre-defined rate. Insurance contract assets are recorded at fair value, which is determined based on the cash surrender value of the insured benefits which is the present value of the guaranteed funded benefits. Insurance contracts are valued using unobservable inputs (Level 3 inputs), primarily by discounting expected future cash flows relating to benefits paid from a notional investment portfolio in order to determine the cash surrender value of the policy. The unobservable inputs consist of estimated future benefits to be paid throughout the duration of the policy and estimated discount rates, which both have an immaterial impact on the fair value estimate of the contract.

[8] Commercial real estate investments are categorized as Level 3 and primarily consist of commercial properties located throughout the various provinces of Canada. The portfolio tracks the IPD Canadian Property Index and invests only in Canadian properties. These investments are recorded at their estimated fair value and are valued using unobservable inputs (Level 3 inputs), primarily by obtaining quarterly independent market appraisals. The unobservable inputs consist of estimated unrealized gains and losses due to changes in real estate market conditions, which have an immaterial impact on the fair value calculations of the real estate investments held.

[9] Commercial mortgage investments are categorized as Level 3 and primarily consist of mortgages on commercial properties located throughout the various provinces of Canada. The portfolio tracks the DEX Conventional Residential Mortgage Index and invests only in Canadian mortgages. These investments are recorded at their estimated fair value and are valued using unobservable inputs (Level 3 inputs), primarily by calculating expected future cash flows at interest rates applicable to new mortgages of similar types and terms. The unobservable inputs consist of estimated unrealized gains and losses due to defaults and other real estate market events and estimated interest rates, which both have an immaterial impact on the fair value calculations of the mortgage investments held.