Other Assets - Narrative (Detail)	12 Months Ended
	Apr. 29, 2018 USD ($) Contract	Apr. 01, 2018 USD ($)	Apr. 30, 2017 USD ($) Contract	May 01, 2016 USD ($)	May 03, 2015 USD ($)
Other Assets [Line Items]
customer relationships, net	$ 2,839,000		$ 664,000	$ 715,000	$ 766,000
Gross carrying amount of customer relationships	3,100,000		868,000
Gross carrying amount of non-compete agreement	$ 2,000,000		$ 2,000,000
Number of life insurance contracts owned | Contract	1		1
Life insurance contracts, death benefits to insured	$ 1,400,000		$ 1,400,000
Life insurance contracts, cash surrender value	393,000		376,000
Prior Acquisition [Member]
Other Assets [Line Items]
customer relationships, net	613,000
Read Window Products LLC [Member] | Trade Names [Member]
Other Assets [Line Items]
Tradename	683,000	$ 683,000
Customer Relationships [Member]
Other Assets [Line Items]
Accumulated amortization	276,000		204,000
Remaining amortization expense for the next fiscal year	301,000
Remaining amortization expense for the second fiscal year	301,000
Remaining amortization expense for the third fiscal year	301,000
Remaining amortization expense for the fourth fiscal year	301,000
Remaining amortization expense for the fifth fiscal year	301,000
Remaining amortization expense for the fiscal year thereafter	$ 1,334,000
Weighted average remaining amortization period	9 years 7 months 6 days
Customer Relationships [Member] | Prior Acquisition [Member]
Other Assets [Line Items]
Useful life	17 years
Customer Relationships [Member] | Read Window Products LLC [Member]
Other Assets [Line Items]
Fair market value of customer relationship		$ 2,247,000
Useful life	9 years
Non-compete Agreement [Member]
Other Assets [Line Items]
Accumulated amortization	$ 1,300,000		$ 1,200,000
Remaining amortization expense for the next fiscal year	75,000
Remaining amortization expense for the second fiscal year	75,000
Remaining amortization expense for the third fiscal year	75,000
Remaining amortization expense for the fourth fiscal year	75,000
Remaining amortization expense for the fifth fiscal year	75,000
Remaining amortization expense for the fiscal year thereafter	$ 378,000
Weighted average remaining amortization period	10 years
Non-compete Agreement [Member] | Prior Acquisition [Member]
Other Assets [Line Items]
Useful life	15 years