Income Taxes - Additional Information (Detail) - USD ($)	3 Months Ended			9 Months Ended
	Apr. 30, 2018	Jan. 31, 2018	Jan. 31, 2017	Apr. 30, 2018	Jan. 31, 2018	Jan. 31, 2017
Income Taxes [Line Items]
Effective tax rate					35.00%
Income tax expense		$ 1,566,000	$ 133,000		$ 3,149,000	$ 1,695,000
Effective tax rate		63.00%			44.80%
Discrete deferred income tax expense		$ 587,000
Tax Cuts and Jobs Act, transition tax for accumulated unrepatriated foreign earnings, provisional income tax expense		528,000
Tax Cuts and Jobs Act, transition tax for accumulated unrepatriated foreign earnings, provisional income tax liability		$ 486,000			$ 486,000
Tax Cuts and Jobs Act, transition tax for accumulated unrepatriated foreign earnings, payment period		8 years
Scenario, Forecast [Member]
Income Taxes [Line Items]
Effective tax rate	21.00%			29.73%