Income Taxes - Additional Information (Detail)	6 Months Ended
	Nov. 30, 2016 USD ($)
Income Tax Contingency [Line Items]
Deferred tax assets	$ 48,800,000
Federal net operating loss and tax credit carryforwards	33,800,000
State net operating loss carryforwards	7,600,000
Differences between financial and tax reporting	7,400,000
Federal [Member]
Income Tax Contingency [Line Items]
Differences between financial and tax reporting	127,000
State [Member]
Income Tax Contingency [Line Items]
Differences between financial and tax reporting	$ 86,000
Minimum [Member] | Federal [Member]
Income Tax Contingency [Line Items]
Net operating loss and tax credit carryforwards life expectancy	11 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