Income Taxes Other (Details) - USD ($)	12 Months Ended
	Apr. 30, 2017	Apr. 30, 2016
Unrecognized tax benefits
State net operating loss carryforwards	$ 57,000
Foreign net operating loss carryforwards	1,144,000
Foreign net operating losses subject to expiration	1,017,000
Activity related to gross unrecognized tax benefits
Beginning balance	9,905,000	$ 8,190,000
Increases related to prior year tax positions	3,000	581,000
Decreases related to prior year tax positions	(26,000)
Increases related to current year tax positions	901,000	1,144,000
Decreases related to lapsing of statute of limitations	(927,000)	(10,000)
Ending balance	9,856,000	9,905,000
Penalties accrued related to uncertain tax positions		$ 55,000
Interest accrued related to uncertain tax positions	16,000
Reversal of uncertain tax position reserve, including interest	968,000
Statute of limitations expiration
Unrecognized tax benefits
Estimated decrease in unrecognized tax benefits in the next twelve months	$ 0