Note 7 - Commitments and Contingencies (Details Textual) - USD ($) $ in Thousands	12 Months Ended
	Apr. 30, 2018	Apr. 30, 2017
Operating Leases, Rent Expense, Total	$ 5,228	$ 5,180
The 3 Year Initial Term [Member]
Lessee, Operating Lease, Term of Contract	3 years
The 5 Year Initial Term [Member]
Lessee, Operating Lease, Term of Contract	5 years
The 10 Year Initial Term [Member]
Lessee, Operating Lease, Term of Contract	10 years
The 25 Year Initial Term [Member]
Lessee, Operating Lease, Term of Contract	25 years