Note 5 - Derivative Financial Instruments - Derivatives Instruments, Statements of Financial Performance and Financial Position (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jan. 27, 2018	Jan. 28, 2017	Jan. 27, 2018	Jan. 28, 2017
Recognized in AOCI:
Gain (loss) before income taxes	$ 2,067	$ 176	$ 6,623	$ (21)
Less income tax provision (benefit)	731	65	2,421	(8)
Net	1,336	111	4,202	(13)
Reclassified from AOCI to cost of sales:
Gain (loss) before income taxes	844	(651)	1,237	(2,844)
Less income tax provision (benefit)	289	(242)	435	(1,056)
Net	555	(409)	802	(1,788)
Reclassified tax effects to provision for income taxes (see Note 6)	515		515
Net change to AOCI	$ 1,296	$ 520	$ 3,915	$ 1,775