Note 2 - Restatement of Previously Issued Financial Statements - Summary of Effects of Restatements (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Sep. 30, 2017	Oct. 01, 2016	Sep. 30, 2017	Oct. 01, 2016	Mar. 31, 2017
Net Sales	$ 338,470	$ 352,606	$ 627,397	$ 624,741
Cost of Products Sold	321,059	321,581	594,451	571,761
Gross Profit	17,411	31,025	32,946	52,980
Operating Income/(Loss)	(1,409)	12,015	(796)	15,592
Earnings/(Loss) Before Income Taxes	(4,842)	9,594	(7,425)	11,464
Income Tax (Benefit) Expense	(1,884)	2,773	(3,487)	3,678
Net (loss) earnings	$ (2,958)	$ 6,821	$ (3,938)	$ 7,786
Earnings Per Common Share-Basic (in dollars per share)	$ (0.30)	$ 0.69	$ (0.40)	$ 0.79
Earnings Per Common Share-Diluted (in dollars per share)	$ (0.30)	$ 0.69	$ (0.40)	$ 0.78
Inventory	$ 859,146	$ 801,684	$ 859,146	$ 801,684	$ 628,935
Total Current Assets	989,368	934,717	989,368	934,717	719,149
Total Assets	1,271,944	1,185,203	1,271,944	1,185,203	978,268
Deferred Revenue	75,150	47,716	75,150	47,716	46,100
Total Current Liabilities	397,567	359,578	397,567	359,578	177,764
Total Liabilities	853,234	785,586	853,234	785,586	553,064
Stockholders' Equity	418,710	399,617	418,710	399,617	425,204
Total Liabilities and Stockholders' Equity	1,271,944	1,185,203	1,271,944	1,185,203	978,268
Previously Reported [Member]
Net Sales	376,308	357,247	656,495	609,861
Cost of Products Sold	355,904	327,035	620,331	559,674
Gross Profit	20,404	30,212	36,164	50,187
Operating Income/(Loss)	1,584	11,202	2,422	12,799
Earnings/(Loss) Before Income Taxes	(1,849)	8,781	(4,207)	8,671
Income Tax (Benefit) Expense	(737)	2,637	(2,256)	2,589
Net (loss) earnings	$ (1,112)	$ 6,144	$ (1,951)	$ 6,082
Earnings Per Common Share-Basic (in dollars per share)	$ (0.11)	$ 0.62	$ (0.20)	$ 0.61
Earnings Per Common Share-Diluted (in dollars per share)	$ (0.11)	$ 0.62	$ (0.20)	$ 0.61
Inventory	$ 802,387	$ 771,996	$ 802,387	$ 771,996	598,056
Total Current Assets	932,609	905,029	932,609	905,029	688,270
Total Assets	1,209,968	1,148,714	1,209,968	1,148,714	946,019
Deferred Revenue	542	550	542	550	545
Total Current Liabilities	322,982	312,466	322,982	312,466	132,277
Total Liabilities	780,214	738,474	780,214	738,474	511,758
Stockholders' Equity	429,754	410,240	429,754	410,240	434,261
Total Liabilities and Stockholders' Equity	1,209,968	1,148,714	1,209,968	1,148,714	946,019
Restatement Adjustment [Member]
Net Sales	(37,838)	(4,641)	(29,098)	14,880
Cost of Products Sold	(34,845)	(5,454)	(25,880)	12,087
Gross Profit	(2,993)	813	(3,218)	2,793
Operating Income/(Loss)	(2,993)	813	(3,218)	2,793
Earnings/(Loss) Before Income Taxes	(2,993)	813	(3,218)	2,793
Income Tax (Benefit) Expense	(1,147)	136	(1,231)	1,089
Net (loss) earnings	$ (1,846)	$ 677	$ (1,987)	$ 1,704
Earnings Per Common Share-Basic (in dollars per share)	$ (0.19)	$ 0.07	$ (0.20)	$ 0.18
Earnings Per Common Share-Diluted (in dollars per share)	$ (0.19)	$ 0.07	$ (0.20)	$ 0.17
Inventory	$ 56,759	$ 29,688	$ 56,759	$ 29,688	30,879
Total Current Assets	56,759	29,688	56,759	29,688	30,879
Total Assets	61,976	36,489	61,976	36,489	32,249
Deferred Revenue	74,608	47,166	74,608	47,166	45,555
Total Current Liabilities	74,585	47,112	74,585	47,112	45,487
Total Liabilities	73,020	47,112	73,020	47,112	41,306
Stockholders' Equity	(11,044)	(10,623)	(11,044)	(10,623)	(9,057)
Total Liabilities and Stockholders' Equity	$ 61,976	$ 36,489	$ 61,976	$ 36,489	$ 32,249