Annual report pursuant to Section 13 and 15(d)

U.S. Pension Plan Investment Allocations by Asset Category (Detail)

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U.S. Pension Plan Investment Allocations by Asset Category (Detail) - USD ($)
$ in Thousands
Aug. 31, 2017
Aug. 31, 2016
Schedule of Pension Plan Assets by Fair Value [Line Items]    
Defined Benefit Plan, Fair Value of Plan Assets $ 40,027 $ 39,489
Percentage of fair value of pension plan assets 100.00% 100.00%
Cash and cash equivalents | Fair Value, Inputs, Level 1    
Schedule of Pension Plan Assets by Fair Value [Line Items]    
Defined Benefit Plan, Fair Value of Plan Assets $ 395 $ 347
Percentage of fair value of pension plan assets 1.00% 0.90%
Fixed Income Securities | Fair Value, Inputs, Level 2    
Schedule of Pension Plan Assets by Fair Value [Line Items]    
Defined Benefit Plan, Fair Value of Plan Assets $ 11,614 $ 11,723
Percentage of fair value of pension plan assets 29.00% 29.70%
Fixed Income Securities | Corporate Bond Securities | Fair Value, Inputs, Level 2    
Schedule of Pension Plan Assets by Fair Value [Line Items]    
Defined Benefit Plan, Fair Value of Plan Assets $ 8,475 $ 8,372
Percentage of fair value of pension plan assets 21.20% 21.20%
Fixed Income Securities | Mutual Funds | Fair Value, Inputs, Level 2    
Schedule of Pension Plan Assets by Fair Value [Line Items]    
Defined Benefit Plan, Fair Value of Plan Assets $ 3,139 $ 3,351
Percentage of fair value of pension plan assets 7.80% 8.50%
Equity Securities | Mutual Funds | Fair Value, Inputs, Level 1    
Schedule of Pension Plan Assets by Fair Value [Line Items]    
Defined Benefit Plan, Fair Value of Plan Assets $ 28,018 $ 27,419
Percentage of fair value of pension plan assets 70.00% 69.40%