Basis of Presentation (Details) - USD ($)	3 Months Ended
	Jul. 31, 2021	Jul. 31, 2020	Apr. 30, 2021	Apr. 30, 2020
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Percentage of LIFO Inventory	43.00%		43.00%
Impairment charges related to goodwill	$ 0	$ 0
Deferred Tax Assets, Net of Valuation Allowance	1,557,000		$ 1,118,000
Net Cash Provided by (Used in) Operating Activities	6,588,000	40,000,000
Cost of sales and distribution	389,138,000	310,520,000
Gross Profit	53,443,000	79,567,000
Operating Income (Loss)	6,456,000	26,226,000
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	4,210,000	21,884,000
Income Tax Expense (Benefit)	1,229,000	5,825,000
Net income	$ 2,981,000	16,059,000
Increase (Decrease) in Deferred Income Taxes		$ (3,000,000)
Earnings Per Share, Basic	$ 0.18	$ 0.95
Earnings Per Share, Diluted	$ 0.18	$ 0.94
Inventories	$ 181,794,000		158,167,000
Total current assets	355,420,000		409,965,000
Assets	1,589,585,000		1,654,399,000
Other Accrued Liabilities, Current	22,029,000		21,913,000
Retained earnings	432,137,000		448,282,000	$ 403,193,000
Stockholders' Equity Attributable to Parent	737,101,000	$ 732,006,000	756,238,000	711,450,000
Liabilities and Equity	1,589,585,000		1,654,399,000
Income taxes payable	326,000	7,855,000
Increase (Decrease) in Inventories	23,532,000	14,968,000
Comprehensive Income (Loss), Net of Tax, Attributable to Parent	2,781,000	16,386,000
Deferred Income Tax Liabilities, Net	43,448,000		42,891,000
Liabilities, Current	198,817,000		220,447,000
Other intangible assets
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Impairment charges related to other intangible assets	$ 0	0
Maximum
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Intangible assets estimated useful lives	6 years
Previously Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Cost of sales and distribution	$ 391,342,000	309,949,000
Gross Profit	51,239,000	80,138,000
Operating Income (Loss)	4,252,000	26,797,000
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	2,006,000	22,455,000
Income Tax Expense (Benefit)	654,000	5,970,000
Net income	$ 1,352,000	16,485,000
Increase (Decrease) in Deferred Income Taxes		$ (2,855,000)
Earnings Per Share, Basic	$ 0.08	$ 0.97
Earnings Per Share, Diluted	$ 0.08	$ 0.97
Inventories	$ 179,590,000		140,282,000
Total current assets	353,216,000		392,080,000
Assets	1,587,381,000		1,636,514,000
Other Accrued Liabilities, Current	21,454,000
Retained earnings	430,508,000		434,940,000	392,281,000
Stockholders' Equity Attributable to Parent	735,472,000	$ 721,520,000	742,896,000	700,538,000
Liabilities and Equity	1,587,381,000		1,636,514,000
Income taxes payable	(249,000)
Increase (Decrease) in Inventories	(21,328,000)	15,539,000
Comprehensive Income (Loss), Net of Tax, Attributable to Parent	1,152,000	16,812,000
Deferred Income Tax Liabilities, Net			38,348,000
Liabilities, Current	198,242,000
Revision of Prior Period, Change in Accounting Principle, Adjustment
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Deferred Tax Assets, Net of Valuation Allowance			4,500,000
Net Cash Provided by (Used in) Operating Activities		1,600,000
Cost of sales and distribution	(2,204,000)
Gross Profit	2,204,000	(571,000)
Operating Income (Loss)	2,204,000	(571,000)
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	2,204,000	(571,000)
Income Tax Expense (Benefit)	575,000	(145,000)
Net income	$ 1,629,000	(426,000)
Increase (Decrease) in Deferred Income Taxes		$ (145,000)
Earnings Per Share, Basic	$ 0.10	$ (0.02)
Earnings Per Share, Diluted	$ 0.10	$ (0.03)
Inventories	$ 2,204,000		17,885,000
Total current assets	2,204,000		17,885,000
Assets	2,204,000		17,885,000
Other Accrued Liabilities, Current	575,000
Retained earnings	1,629,000		13,342,000	10,912,000
Stockholders' Equity Attributable to Parent	1,629,000	$ 10,486,000	13,342,000	$ 10,912,000
Liabilities and Equity	2,204,000		17,885,000
Income taxes payable	575,000
Increase (Decrease) in Inventories	(2,204,000)	571,000
Comprehensive Income (Loss), Net of Tax, Attributable to Parent	1,629,000	$ (426,000)
Deferred Income Tax Liabilities, Net			$ 4,543,000
Liabilities, Current	$ 575,000