Condensed Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 6,657	$ 8,685
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	4,765	4,712
Provision for doubtful accounts	3	(191)
Provision for warranty and returns	(410)	(6)
Stock compensation	1,973	1,390
Gain on disposal of property and equipment	(5)	0
Bond premium amortization	601	675
Cash provided (used) by changes in operating assets and liabilities
Accounts receivable	2,416	(3,981)
Inventories	(2,267)	(578)
Prepaid expenses and other assets	(800)	1,234
Accounts payable	382	(244)
Accrued liabilities	(2,557)	(2,949)
Income taxes, including excess tax benefits and deferred income taxes	1,956	2,017
Net cash provided by operating activities	12,714	10,764
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of property and equipment	(5,908)	(5,831)
Proceeds from sale of assets	5	0
Intangible assets acquired	(120)	(355)
Purchases of investment securities	(36,908)	(19,131)
Proceeds from sale of investment securities	30,936	18,317
Net cash used by investing activities	(11,995)	(7,000)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from exercise of stock options	4,202	2,904
Proceeds from employee stock purchase plan	1,384	1,267
Tax benefits from exercise of stock options	1,178	1,034
Payments for Repurchase of Common Stock	(5,835)	0
Net cash provided by financing activities	929	5,205
Effect of exchange rate changes on cash	(47)	(1,238)
NET INCREASE IN CASH AND CASH EQUIVALENTS	1,601	7,731
CASH AND CASH EQUIVALENTS, beginning of period	226,022	146,900
CASH AND CASH EQUIVALENTS, end of period	227,623	154,631
NON-CASH INVESTING ACTIVITIES
Accrued liabilities for property and equipment	$ 1,008	$ 196