Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
CASH FLOWS FROM OPERATING ACTIVITIES:
Net Income	$ 44,985	$ 26,335	$ 40,418
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	18,073	19,447	19,506
Provision for doubtful accounts	54	34	185
Provision for warranty and returns	52	(360)	671
Stock compensation	12,827	9,592	5,434
(Gain) loss on disposal of property and equipment	(1,106)	8	(36)
Bond premium amortization	1,670	2,188	2,715
Impairment of assets held for sale	4,139	0	0
Cash provided (used) by changes in operating assets and liabilities
Accounts receivable	(20,515)	4,912	3,556
Inventories	(8,337)	(3,836)	2,319
Prepaid expenses and other assets	(1,832)	1,970	(383)
Accounts payable	3,118	(621)	(31)
Accrued liabilities	9,454	2,344	(2,215)
Income taxes, including excess tax benefits and deferred income taxes	(7,717)	(1,373)	(6,413)
Net cash provided by operating activities	54,865	60,640	65,726
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of property and equipment	(12,984)	(16,604)	(18,415)
Proceeds from sale of assets	3,592	5	49
Intangible asset additions	(951)	(989)	(1,080)
Business acquisitions, net of cash acquired	(56,786)	0	0
Proceeds from sale of business	28,970	0	0
Purchases of investment securities	(56,137)	(93,588)	(86,022)
Proceeds from sale of investment securities	83,054	89,426	92,348
Net cash used by investing activities	(11,242)	(21,750)	(13,120)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from exercise of stock options	15,042	16,998	18,004
Proceeds from employee stock purchase plan	2,162	2,485	2,457
Excess tax benefit from exercise of stock options	9,330	5,700	6,966
Purchase of treasury stock	(1,523)	(5,836)	(3,033)
Net cash provided by financing activities	25,011	19,347	24,394
Effect of exchange rate changes on cash	(8,282)	(8,447)	2,122
NET INCREASE IN CASH AND CASH EQUIVALENTS	60,352	49,790	79,122
CASH AND CASH EQUIVALENTS, beginning of period	275,812	226,022	146,900
CASH AND CASH EQUIVALENTS, end of period	336,164	275,812	226,022
SUPPLEMENTAL DISCLSOURE OF CASH FLOW INFORMATION
Cash paid during the year for income taxes	22,998	8,668	12,172
NON-CASH INVESTING ACTIVITIES
Accrued liabilities for property and equipment	182	789	212
Fair value of assets acquired	60,693	0	0
Liabilities assumed	$ (3,907)	$ 0	$ 0