Note 2 - Revenue Recognition - Impact of Topic 606 (Details) - USD ($) $ / shares in Units, $ in Thousands	2 Months Ended	3 Months Ended			9 Months Ended
	Sep. 03, 2018	Sep. 30, 2018	Sep. 30, 2017		Sep. 30, 2018	Sep. 30, 2017		Dec. 31, 2017
Accounts receivable		$ 59,887			$ 59,887			$ 38,037
Inventories		136,790			136,790			99,281
Other current assets		12,876			12,876			12,762
Total current assets		557,401			557,401			449,170
Deferred tax assets, net		12,852			12,852			15,917
Total assets		763,157			763,157			652,569
Accrued liabilities		34,908			34,908			27,507
Total current liabilities		85,507			85,507			65,917
Total liabilities		152,993			152,993			130,562
Retained earnings		180,819			180,819			143,608
Total stockholders' equity		610,164			610,164			522,007
Total liabilities and stockholders' equity		763,157			763,157			$ 652,569
Revenue		159,975	$ 128,939	[1]	428,885	$ 341,499	[1]
Cost of revenue		70,957	58,083		190,810	154,377
Gross profit		89,018	70,856		238,075	187,122
Income from operations		33,493	23,832		80,411	52,371
Income before income taxes		36,207	25,087		85,798	56,244
Income tax provision		4,639	1,445		8,168	3,112
Net income	$ 31,568	$ 31,568	$ 23,642		$ 77,630	$ 53,132
Basic (in dollars per share)		$ 0.75	$ 0.57		$ 1.84	$ 1.29
Net income per share - diluted (in dollars per share)		$ 0.71	$ 0.54		$ 1.75	$ 1.22
Comprehensive income	27,533	$ 27,533	$ 25,364		$ 70,077	$ 57,689
Accounts receivable					(22,752)	(16,505)
Inventories					(37,496)	(28,384)
Other assets					(665)	1,696
Accrued liabilities					4,635	7,276
Income tax liabilities					528	$ 1,249
Calculated under Revenue Guidance in Effect before Topic 606 [Member]
Accounts receivable		61,430			61,430
Inventories		137,129			137,129
Other current assets		10,556			10,556
Total current assets		556,963			556,963
Deferred tax assets, net		12,953			12,953
Total assets		762,820			762,820
Accrued liabilities		35,190			35,190
Total current liabilities		85,789			85,789
Total liabilities		153,275			153,275
Retained earnings		180,200			180,200
Total stockholders' equity		609,545			609,545
Total liabilities and stockholders' equity		762,820			762,820
Revenue		159,723			428,440
Cost of revenue		70,848			190,668
Gross profit		88,875			237,772
Income from operations		33,350			80,108
Income before income taxes		36,064			85,495
Income tax provision		4,609			8,104
Net income	31,455	$ 31,455			$ 77,391
Basic (in dollars per share)		$ 0.74			$ 1.84
Net income per share - diluted (in dollars per share)		$ 0.70			$ 1.74
Comprehensive income	27,420				$ 69,838
Accounts receivable					(23,394)
Inventories					(37,835)
Other assets					1,563
Accrued liabilities					3,691
Income tax liabilities					464
Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Accounting Standards Update 2014-09 [Member]
Accounts receivable		$ (1,543)			(1,543)
Inventories		(339)			(339)
Other current assets		2,320			2,320
Total current assets		438			438
Deferred tax assets, net		(101)			(101)
Total assets		337			337
Accrued liabilities		(282)			(282)
Total current liabilities		(282)			(282)
Total liabilities		(282)			(282)
Retained earnings		619			619
Total stockholders' equity		619			619
Total liabilities and stockholders' equity		337			337
Revenue		252			445
Cost of revenue		109			142
Gross profit		143			303
Income from operations		143			303
Income before income taxes		143			303
Income tax provision		30			64
Net income	113	$ 113			$ 239
Basic (in dollars per share)		$ 0.01
Net income per share - diluted (in dollars per share)		$ 0.01			$ 0.01
Comprehensive income	$ 113				$ 239
Accounts receivable					642
Inventories					339
Other assets					(2,228)
Accrued liabilities					944
Income tax liabilities					$ 64

[1] 2017 amounts have not been adjusted under the modified retrospective method.