Condensed Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 8,685	$ 7,601
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	4,712	4,777
Provision for doubtful accounts	(191)	(263)
Provision for warranty and returns	(6)	312
Stock compensation	1,390	1,231
Loss (gain) on disposal of property and equipment	0	27
Bond premium amortization	675	357
Cash provided (used) by changes in operating assets and liabilities
Accounts receivable	(3,981)	1,931
Inventories	(578)	3,768
Prepaid expenses and other assets	1,234	898
Accounts payable	(244)	(1,610)
Accrued liabilities	(2,949)	(2,608)
Prepaid and deferred income taxes	2,017	1,915
Net cash provided by operating activities	10,764	18,336
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of property and equipment	(5,831)	(3,632)
Proceeds from sale of asset	0	10
Intangible assets acquired	(355)	(287)
Purchases of investment securities	(19,131)	(22,424)
Proceeds from sale of investment securities	18,317	21,442
Net cash used by investing activities	(7,000)	(4,891)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from exercise of stock options	2,904	5,684
Proceeds from employee stock purchase plan	1,267	1,081
Tax benefits from exercise of stock options	1,034	1,626
Net cash provided by financing activities	5,205	8,391
Effect of exchange rate changes on cash	(1,238)	677
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	7,731	22,513
CASH AND CASH EQUIVALENTS, beginning of period	146,900
CASH AND CASH EQUIVALENTS, end of period	154,631
NON-CASH INVESTING ACTIVITIES
Accrued liabilities for property and equipment	$ 196	$ 588