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, 2018
Aug. 31, 2017
Schedule of Pension Plan Assets by Fair Value [Line Items]    
Defined Benefit Plan, Fair Value of Plan Assets $ 40,244 $ 40,027
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 $ 559 $ 395
Percentage of fair value of pension plan assets 1.40% 1.00%
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 $ 19,921 $ 11,614
Percentage of fair value of pension plan assets 49.50% 29.00%
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 $ 19,107 $ 8,475
Percentage of fair value of pension plan assets 47.50% 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 $ 814 $ 3,139
Percentage of fair value of pension plan assets 2.00% 7.80%
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 $ 19,764 $ 28,018
Percentage of fair value of pension plan assets 49.10% 70.00%