Note 2 - Revenue Recognition - Impact of Topic 606 (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017		Dec. 31, 2017
Assets:
Accounts receivable	$ 48,241			$ 38,037
Inventory	111,897			99,281
Other current assets	16,707			12,762
Deferred tax assets	15,840			15,917
Total assets	697,767			652,569
Liabilities and Stockholders' Equity:
Accrued liabilities	32,730			27,507
Retained earnings	152,257			143,608
Total liabilities and stockholders' Equity	697,767			$ 652,569
Revenue	129,150	$ 100,362	[1]
Cost of revenue	57,655	45,520
Gross profit	71,495	54,842
Income from operations	22,037	13,570
Income before income taxes	22,477	14,951
Income tax provision	621	474
Net income	21,856	14,477
Comprehensive income	25,085	15,985
Cash flows from operating activities:
Accounts receivable	(11,103)	(3,865)
Inventories	(12,590)	(7,057)
Other assets	(3,954)	(1,465)
Accrued liabilities	4,998	2,402
Income tax liabilities	(2,236)	$ (753)
Calculated under Revenue Guidance in Effect before Topic 606 [Member]
Assets:
Accounts receivable	49,121
Inventory	112,215
Other current assets	14,602
Deferred tax assets	15,941
Total assets	696,961
Liabilities and Stockholders' Equity:
Accrued liabilities	32,406
Retained earnings	151,775
Total liabilities and stockholders' Equity	696,961
Revenue	128,959
Cost of revenue	57,595
Gross profit	71,364
Income from operations	21,906
Income before income taxes	22,346
Income tax provision	594
Net income	21,752
Comprehensive income	24,981
Cash flows from operating activities:
Accounts receivable	(11,082)
Inventories	(12,908)
Other assets	(1,940)
Accrued liabilities	3,412
Income tax liabilities	(2,263)
Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Accounting Standards Update 2014-09 [Member]
Assets:
Accounts receivable	(880)
Inventory	(318)
Other current assets	2,105
Deferred tax assets	(101)
Total assets	806
Liabilities and Stockholders' Equity:
Accrued liabilities	324
Retained earnings	482
Total liabilities and stockholders' Equity	806
Revenue	191
Cost of revenue	60
Gross profit	131
Income from operations	131
Income before income taxes	131
Income tax provision	27
Net income	104
Comprehensive income	104
Cash flows from operating activities:
Accounts receivable	(21)
Inventories	318
Other assets	(2,014)
Accrued liabilities	1,586
Income tax liabilities	$ 27

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