Acquisition of RSI Home Products, Inc. (the "RSI Acquisition") (Narrative) (Details) - USD ($)		1 Months Ended	3 Months Ended		9 Months Ended
	Dec. 29, 2017	Jan. 31, 2018	Jan. 31, 2018	Jan. 31, 2017	Jan. 31, 2018	Jan. 31, 2017	Apr. 30, 2017	May 01, 2016
Business Acquisition [Line Items]
Acquisition, cash consideration, net of cash acquired					$ 57,200,000	$ 0
Goodwill, net		$ 765,743,000	$ 765,743,000		765,743,000		$ 0
Net sales			292,791,000	$ 249,285,000	844,387,000	771,511,000
Operating income (loss)			7,720,000	21,601,000	69,369,000	81,854,000
Cost of sales			242,412,000	$ 197,689,000	$ 678,179,000	$ 604,446,000
Effective income tax rate, proportional federal rate					34.40%	40.40%
Amortization of debt					$ 20,000,000	$ 20,500,000
Amortization expense, debt issuance costs					$ 6,700,000
Debt issuance, amortization period					5 years
Debt interest expense, net of tax					$ 3,000,000	3,300,000
Acquisition, transaction costs, add-dack, net of tax					6,900,000	$ 500,000
Revolving loan facility
Business Acquisition [Line Items]
Proceeds from loan	$ 50,000,000
Outstanding on the Revolving Facility		30,000,000	$ 30,000,000		30,000,000
Credit Agreement | Revolving loan facility
Business Acquisition [Line Items]
Outstanding on the Revolving Facility								$ 300,000,000
RSI Home Products, Inc.
Business Acquisition [Line Items]
Acquisition, indebtedness assumed	589,000,000
Consideration transferred, acquisition	553,200,000
Acquisition, cash consideration, net of cash acquired	$ 363,300,000
Acquisition, shares issued (in shares)	1,457,568
Acquisition, shares issued, amount	$ 189,800,000
Acquisition, share price	$ 130.25
Goodwill, net	$ 765,743,000
Customer receivables	54,649,000
Customer receivables, allowance for doubtful accounts	100,000
Net sales		38,600,000
Operating income (loss)		(4,900,000)
Acquisition, transaction costs					10,200,000
RSI Home Products, Inc. | Fair value adjustment to inventory
Business Acquisition [Line Items]
Cost of sales		$ 6,300,000			$ 4,100,000
RSI Home Products, Inc. | Revolving loan facility
Business Acquisition [Line Items]
Proceeds from loan	50,000,000
RSI Home Products, Inc. | Revolving Facility | Revolving loan facility
Business Acquisition [Line Items]
Credit facility, maximum borrowing capacity	100,000,000
RSI Home Products, Inc. | Revolving Facility | Letter of credit
Business Acquisition [Line Items]
Credit facility, maximum borrowing capacity	25,000,000
RSI Home Products, Inc. | Term loan | Initial Term Loan
Business Acquisition [Line Items]
Credit facility, maximum borrowing capacity	$ 250,000,000
Debt term	5 years
RSI Home Products, Inc. | Term loan | Delayed Draw Term Loan
Business Acquisition [Line Items]
Credit facility, maximum borrowing capacity	$ 250,000,000