Note 11 - Comprehensive Income - Components of Comprehensive Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Apr. 30, 2019	Apr. 30, 2018	Apr. 30, 2017
Other comprehensive income (loss), available-for-sale securities adjustment, amount before tax	$ 1,133	$ 285	$ 515
Other comprehensive income (loss), available-for-sale securities, tax expense	(238)	40	(182)
Other comprehensive income (loss), available-for-sale securities adjustment, amount net of tax	895
Change in unrealized gains on securities, net of taxes	895	325	333
Change in unrealized gains (losses) on securities, amount before tax		437	554
Change in unrealized gains (losses) on securities, tax expense		8	(196)
Change in unrealized gains (losses) on securities, amount net of tax		445	358
Less: Gains realized in net income, amount before tax		(152)	(39)
Less: Gains realized in net income, tax expense		32	14
Less: Gains realized in net income, amount net of tax		(120)	(25)
Other comprehensive income (loss), available-for-sale securities adjustment, amount before tax	1,133	285	515
Other comprehensive income (loss), available-for-sale securities, tax expense	(238)	40	(182)
Other comprehensive income (loss), available-for-sale securities adjustment, amount net of tax	$ 895	$ 325	$ 333