Acquisition of RSI Home Products, Inc. (the "RSI Acquisition") (Narrative) (Details) - USD ($)		3 Months Ended								4 Months Ended	12 Months Ended
	Dec. 29, 2017	Apr. 30, 2019	Jan. 31, 2019	Oct. 31, 2018	Jul. 31, 2018	Apr. 30, 2018	Jan. 31, 2018	Oct. 31, 2017	Jul. 31, 2017	Apr. 30, 2018	Apr. 30, 2019	Apr. 30, 2018	Apr. 30, 2017	Feb. 12, 2018	May 01, 2016
Business Acquisition [Line Items]
Cash consideration, net of cash acquired											$ 7,182,000	$ 57,200,000	$ 0
Goodwill, net		$ 767,612,000				$ 767,451,000				$ 767,451,000	767,612,000	767,451,000
Customer receivables	$ 57,100,000
Allowance for returns and discounts	2,400,000
Net sales		407,399,000	$ 384,080,000	$ 424,878,000	$ 428,962,000	405,887,000	$ 292,791,000	$ 274,769,000	$ 276,827,000		1,645,319,000	1,250,274,000	1,030,248,000
Operating profit											141,694,000	107,705,000	108,238,000
Charge to cost of sales as a result of the step up of inventory											$ 1,298,846,000	994,871,000	805,612,000
Transaction costs												$ 8,500,000	$ 1,600,000
Statutory tax rate											21.00%	30.40%	35.00%
Amortization expense, net of tax												$ 20,000,000	$ 27,200,000
Interest expense, net of tax												2,400,000	$ 4,400,000
RSI Home Products, Inc. [Member]
Business Acquisition [Line Items]
Indebtedness assumed (including accrued interest)	589,000,000
Total accounting consideration paid	554,232,000
Cash consideration, net of cash acquired	$ 364,400,000
Newly issued shares (shares)	1,457,568
Value of newly issued common stock	$ 189,800,000
Price per share (usd per share)	$ 130.25
Goodwill, net	$ 767,612,000
Allowance for doubtful accounts	100,000
Net sales										177,700,000
Operating profit										9,100,000
Transaction costs											$ 12,900,000
Senior Notes [Member] | RSI Home Products, Inc. [Member]
Business Acquisition [Line Items]
Debt issued														$ 350,000,000
Revolving Credit Facility [Member]
Business Acquisition [Line Items]
Proceeds from term loan	50,000,000
Borrowed under the Credit Agreement		0				0				0	0	0
Revolving Credit Facility [Member] | RSI Home Products, Inc. [Member]
Business Acquisition [Line Items]
Proceeds from term loan	50,000,000
Revolving Credit Facility [Member] | Revolving Facility [Member] | RSI Home Products, Inc. [Member]
Business Acquisition [Line Items]
Line of credit facility, maximum borrowing capacity	100,000,000
Revolving Credit Facility [Member] | Credit Agreement [Member]
Business Acquisition [Line Items]
Borrowed under the Credit Agreement															$ 300,000,000
Letter of Credit [Member] | Revolving Facility [Member] | RSI Home Products, Inc. [Member]
Business Acquisition [Line Items]
Line of credit facility, maximum borrowing capacity	25,000,000
Loans Payable [Member] | Initial Term Loan [Member]
Business Acquisition [Line Items]
Debt issued	250,000,000
Borrowed under the Credit Agreement		170,000,000				230,000,000				230,000,000	170,000,000	230,000,000
Loans Payable [Member] | Initial Term Loan [Member] | RSI Home Products, Inc. [Member]
Business Acquisition [Line Items]
Line of credit facility, maximum borrowing capacity	$ 250,000,000
Loan facility term	5 years
Loans Payable [Member] | Delayed Draw Term Loan [Member]
Business Acquisition [Line Items]
Debt issued	$ 250,000,000
Borrowed under the Credit Agreement		$ 170,000,000				$ 230,000,000				230,000,000	$ 170,000,000	230,000,000
Loans Payable [Member] | Delayed Draw Term Loan [Member] | RSI Home Products, Inc. [Member]
Business Acquisition [Line Items]
Line of credit facility, maximum borrowing capacity	$ 250,000,000
Fair Value Adjustment to Inventory [Member] | RSI Home Products, Inc. [Member]
Business Acquisition [Line Items]
Charge to cost of sales as a result of the step up of inventory										$ 6,300,000		$ 4,100,000
Pro Forma [Member]
Business Acquisition [Line Items]
Statutory tax rate												34.40%	40.40%