Note 6 - Recently Issued Accounting Pronouncements (Details Textual) - USD ($)	3 Months Ended		9 Months Ended
	Jan. 27, 2018	Jan. 28, 2017	Jan. 27, 2018	Jan. 28, 2017
Reclassified Tax Effects from AOCI to Income Tax Provision	$ 515,000		$ 515,000
Reclassification of Excess Tax Benefits from Financing to Operating Activities [Member] | Nine Months Ended January 28, 2017 [Member]
Prior Period Reclassification Adjustment			153,000
Accounting Standards Update 2016-09 [Member]
Income Tax Expense (Benefit), Extraordinary Items	(120,000)		(681,000)
Reclassification of Deferred Taxes from Current to Non-current [Member] | April 29, 2017 [Member]
Prior Period Reclassification Adjustment			$ 3,900,000
Accounting Standards Update 2018-02 [Member]
Reclassified Tax Effects from AOCI to Income Tax Provision	$ 0