Condensed Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 12,535	$ 16,052
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	9,666	9,589
Provision for doubtful accounts	3	40
Provision for warranty and returns	(597)	16
Stock compensation	4,459	2,822
Loss (gain) on disposal of property and equipment	2	(20)
Bond premium amortization	1,060	1,338
Cash provided (used) by changes in operating assets and liabilities
Accounts receivable	4,786	(623)
Inventories	(3,456)	(186)
Prepaid expenses and other assets	548	649
Accounts payable	(134)	208
Accrued liabilities	498	(1,035)
Income taxes, including excess tax benefits and deferred income taxes	(95)	(2,894)
Net cash provided by operating activities	29,275	25,956
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of property and equipment	(12,729)	(11,781)
Proceeds from sale of asset	5	20
Intangible assets acquired	(377)	(633)
Purchases of investment securities	(60,090)	(45,368)
Proceeds from sale of investment securities	49,863	49,650
Net cash used by investing activities	(23,328)	(8,112)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from exercise of stock options	7,016	3,921
Proceeds from employee stock purchase plan	1,384	1,267
Tax benefits from exercise of stock options	1,985	3,084
Purchase of treasury stock	(5,835)	(1,792)
Net cash provided by financing activities	4,550	6,480
Effect of exchange rate changes on cash	(568)	(636)
NET INCREASE IN CASH AND CASH EQUIVALENTS	9,929	23,688
CASH AND CASH EQUIVALENTS, beginning of period	226,022	146,900
CASH AND CASH EQUIVALENTS, end of period	235,951	170,588
NON-CASH INVESTING ACTIVITIES
Accrued liabilities for property and equipment	$ 140	$ 228