Organization and Significant Accounting Policies Other (Details) - USD ($)	3 Months Ended		9 Months Ended
	Jan. 27, 2018	Jan. 28, 2017	Jan. 27, 2018	Jan. 28, 2017	Apr. 30, 2017
Government Contracts
Reserves for incurred cost claim audits	$ 77,000		$ 77,000		$ 0
Denominator for basic (loss) earnings per share:
Weighted-average common shares outstanding, excluding unvested restricted stock (in shares)	23,515,622	23,082,974	23,443,673	23,029,546
Dilutive effect of employee stock options and unvested restricted stock (in shares)			331,273
Denominator for diluted (loss) earnings per share (in shares)	23,515,622	23,082,974	23,774,946	23,029,546
Number of shares reserved for issuance that are anti-dilutive	379,749	222,071	27,139	246,093