Condensed Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 9,686	$ 6,657
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	4,629	4,765
Provision for doubtful accounts	0	3
Provision for warranty and returns	31	(410)
Stock compensation	2,813	1,973
Loss (gain) on disposal of property and equipment	2	(5)
Bond premium amortization	943	601
Cash provided (used) by changes in operating assets and liabilities
Accounts receivable	(4,947)	2,416
Inventories	(1,785)	(2,267)
Prepaid expenses and other assets	(980)	(800)
Accounts payable	1,951	382
Accrued liabilities	3,300	(2,557)
Income taxes, including excess tax benefits and deferred income taxes	(2,392)	1,956
Net cash provided by operating activities	13,251	12,714
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of property and equipment	(2,357)	(5,908)
Proceeds from sale of asset	0	5
Intangible assets acquired	(208)	(120)
Purchases of investment securities	(9,205)	(36,908)
Proceeds from sale of investment securities	31,785	30,936
Net cash provided (used) by investing activities	20,015	(11,995)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from exercise of stock options	4,777	4,202
Proceeds from employee stock purchase plan	1,041	1,384
Tax benefits from exercise of stock options	3,059	1,178
Purchase of treasury stock	(1,435)	(5,835)
Net cash provided by financing activities	7,442	929
Effect of exchange rate changes on cash	(7,987)	(47)
NET INCREASE IN CASH AND CASH EQUIVALENTS	32,721	1,601
CASH AND CASH EQUIVALENTS, beginning of period	275,812	226,022
CASH AND CASH EQUIVALENTS, end of period	308,533	227,623
NON-CASH INVESTING ACTIVITIES
Accrued liabilities for property and equipment	$ 144	$ 1,008