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		9 Months Ended
	Jan. 31, 2017	Jan. 31, 2016	Jan. 31, 2017	Jan. 31, 2016
Change in unrealized gains (losses) on securities			$ 271	$ (147)
Change in unrealized gains (losses) on securities			(96)	52
Change in unrealized gains (losses) on securities			175	(95)
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, before Tax, Portion Attributable to Parent			232	(237)
Other comprehensive income (loss), available-for-sale securities, tax (expense)/(benefit)			(82)	84
Other comprehensive income (loss), available-for-sale securities adjustment, net of tax	$ 290	$ (127)	150	(153)
Gains Realized in Net Income [Member]
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, before Tax			(39)	(105)
Less: Gains realized in net income			14	37
Less: Gains realized in net income			(25)	(68)
Add: Losses realized in net income, tax			$ (14)	(37)
Losses Realized in Net Income [Member]
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, before Tax				15
Less: Gains realized in net income				5
Less: Gains realized in net income				10
Add: Losses realized in net income, tax				$ (5)