Condensed Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 16,052	$ 16,750
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	9,589	9,533
Provision for doubtful accounts	40	(152)
Provision for warranty and returns	16	247
Stock compensation	2,822	3,042
Loss (gain) on disposal of property and equipment	(20)	27
Bond premium amortization	1,338	985
Cash provided (used) by changes in operating assets and liabilities
Accounts receivable	(623)	(850)
Inventories	(186)	3,707
Prepaid expenses and other assets	649	821
Accounts payable	208	(608)
Accrued liabilities	(1,035)	1,582
Prepaid and deferred income taxes	(2,894)	(3,612)
Net cash provided by operating activities	25,956	31,472
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of property and equipment	(11,781)	(8,222)
Proceeds from sale of asset	20	10
Intangible assets acquired	(633)	(620)
Purchases of investment securities	(45,368)	(53,966)
Proceeds from sale of investment securities	49,650	41,062
Net cash used by investing activities	(8,112)	(21,736)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from exercise of stock options	3,921	9,333
Proceeds from employee stock purchase plan	1,267	1,081
Tax benefits from exercise of stock options	3,084	2,758
Treasury stock acquired - share awards swap for tax payments	1,792	0
Net cash provided by financing activities	6,480	13,172
Effect of exchange rate changes on cash	(636)	(938)
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	23,688	21,970
CASH AND CASH EQUIVALENTS, beginning of period	146,900	99,590
CASH AND CASH EQUIVALENTS, end of period	170,588	121,560
NON-CASH INVESTING ACTIVITIES
Accrued liabilities for property and equipment	$ 228	$ 77