Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
CASH FLOWS FROM OPERATING ACTIVITIES:
Net Income	$ 41,281	$ 44,669	$ 29,923
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	19,001	18,294	17,345
Provision for doubtful accounts	(237)	648	443
Provision for warranty and returns	220	0	0
Stock compensation	5,563	4,016	3,471
Loss (gain) on disposal of property and equipment	212	(42)	338
Gain on sale of assets	0	(14,242)	0
Bond premium amortization	2,585	1,294	1,092
Cash provided (used) by changes in operating assets and liabilities
Accounts receivable	(5,395)	6,232	(6,378)
Inventories	4,573	3,170	(3,670)
Prepaid expenses and other assets	(415)	(920)	(2,518)
Accounts payable	(1,536)	2,673	(8,222)
Accrued liabilities	1,199	1,684	1,946
Deferred revenue	0	(254)	(2,135)
Income taxes, including excess tax benefits and deferred income taxes	(780)	(2,735)	1,460
Net cash provided by operating activities	66,271	64,487	33,095
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of property and equipment	(19,160)	(15,824)	(23,171)
Proceeds from Sale of Assets	10	16,201	893
Proceeds from insurance	0	2,781	622
Intangible asset additions	(1,145)	0	0
Purchases of investment securities	(98,876)	(90,502)	(23,382)
Proceeds from sale of investment securities	77,798	41,610	64,670
Net cash provided (used) by investing activities	(41,373)	(45,734)	19,632
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from exercise of stock options	14,844	7,974	2,517
Proceeds from employee stock purchase plan	2,220	1,828	1,576
Tax benefits from exercise of stock options	4,567	4,288	1,680
Purchase of treasury stock	0	(11,956)	(28,648)
Net cash provided (used) by financing activities	21,631	2,134	(22,875)
Effect of exchange rate changes on cash	781	(147)	(2,250)
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	47,310	20,740	27,602
CASH AND CASH EQUIVALENTS, beginning of period	99,590	78,850	51,248
CASH AND CASH EQUIVALENTS, end of period	146,900	99,590	78,850
SUPPLEMENTAL DISCLSOURE OF CASH FLOW INFORMATION
Cash paid during the year for income taxes	16,741	20,110	15,249
NON-CASH INVESTING ACTIVITIES
Accrued liabilities for property and equipment	$ 427	$ 418	$ 716