Note 6 - Comprehensive Income - Components of Comprehensive Income That Are Included in Consolidated Statement of Changes in Shareholders' Equity (Details) - USD ($) $ in Thousands	3 Months Ended
	Jul. 31, 2017	Jul. 31, 2016
Change in unrealized gains (losses) on securities	$ 142	$ 238
Change in unrealized gains (losses) on securities	(50)	(84)
Change in unrealized gains (losses) on securities	92	154
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, before Tax, Portion Attributable to Parent	142	238
Other comprehensive income (loss), available-for-sale securities, tax (expense)/(benefit)	(50)	(84)
Other comprehensive income (loss), available-for-sale securities adjustment, net of tax	$ 92	$ 154