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Income Taxes - Additional Information (Detail)
$ in Millions
 3 Months Ended
Aug. 31, 2015
USD ($)
Income Tax Contingency [Line Items]  
Deferred tax assets $ 50
Federal net operating loss and tax credit carryforwards 35
State net operating loss carryforwards 8
Differences between financial and tax reporting $ 7
Minimum [Member] | Federal [Member]  
Income Tax Contingency [Line Items]  
Net operating loss and tax credit carryforwards life expectancy 13 years
Minimum [Member] | State [Member]  
Income Tax Contingency [Line Items]  
Net operating loss and tax credit carryforwards life expectancy 1 year
Maximum [Member] | Federal [Member]  
Income Tax Contingency [Line Items]  
Net operating loss and tax credit carryforwards life expectancy 20 years
Maximum [Member] | State [Member]  
Income Tax Contingency [Line Items]  
Net operating loss and tax credit carryforwards life expectancy 20 years