Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 23,256	$ 12,535
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	9,026	9,666
Provision for doubtful accounts	53	3
Provision for warranty and returns	38	(597)
Stock compensation	5,947	4,459
Loss (gain) on disposal of property and equipment	(33)	2
Bond premium amortization	1,223	1,060
Cash provided (used) by changes in operating assets and liabilities
Accounts receivable	(5,529)	4,786
Inventories	(2,267)	(3,456)
Prepaid expenses and other assets	(1,375)	548
Accounts payable	1,894	(134)
Accrued liabilities	(1,027)	498
Income taxes, including excess tax benefits and deferred income taxes	(5,456)	(95)
Net cash provided by operating activities	25,750	29,275
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of property and equipment	(5,005)	(12,729)
Proceeds from sale of asset	34	5
Intangible assets acquired	(440)	(377)
Purchases of investment securities	(17,092)	(60,090)
Proceeds from sale of investment securities	49,555	49,863
Net cash provided (used) by investing activities	27,052	(23,328)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from exercise of stock options	5,797	7,016
Proceeds from employee stock purchase plan	1,041	1,384
Tax benefits from exercise of stock options	3,425	1,985
Purchase of treasury stock	(1,435)	(5,835)
Net cash provided by financing activities	8,828	4,550
Effect of exchange rate changes on cash	(6,350)	(568)
NET INCREASE IN CASH AND CASH EQUIVALENTS	55,280	9,929
CASH AND CASH EQUIVALENTS, beginning of period	275,812	226,022
CASH AND CASH EQUIVALENTS, end of period	331,092	235,951
NON-CASH INVESTING ACTIVITIES
Accrued liabilities for property and equipment	$ 232	$ 140