CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Net income	$ 3,695	$ 2,952	$ 1,184	$ 6,479
Adjustments to reconcile net income to net cash (used in) provided by operating activities:
Depreciation and amortization	3,949	3,533	7,753	7,055
Stock-based compensation	2,412	2,571	4,844	5,214
Deferred income tax expense	726	376	1,426	929
Excess income tax expense (benefit) from employee stock-based awards	15	(2,476)	289	(2,773)
Loss on disposal of assets	65	0	83	0
Other	(1,279)	(49)	(1,081)	183
Changes in operating assets and liabilities:
Accounts receivable, net	(6,403)	830	1,692	(3,183)
Inventories, net	(1,279)	(1,860)	(3,683)	(1,727)
Other assets	(747)	(1,671)	(1,643)	(1,631)
Accounts payable	(1,202)	555	(2,933)	69
Accrued liabilities	(3,320)	4,811	(1,543)	(1,215)
Deferred revenue	(293)	(50)	(30)	93
Cash flows from investing activities:
Purchases of available-for-sale securities	(2,497)	(1,496)	(5,492)	(10,495)
Sales and maturities of available-for-sale securities	3,603	21,490	16,636	30,005
Purchase of property and equipment	(5,431)	(3,761)	(8,222)	(5,357)
Proceeds from sale of assets	0	0	31	0
Acquired technology rights	0	(291)	(930)	(291)
Net cash (used in) provided by investing activities	(4,325)	15,942	2,023	13,862
Cash flows from financing activities:
Payments on debt	(1,105)	(1,025)	(1,105)	(1,025)
Proceeds from issuance of common stock	517	1,706	1,918	2,363
Payments for stock repurchases	(8,568)	(4,432)	(14,343)	(9,880)
Excess income tax (expense) benefit from employee stock-based awards	(15)	2,476	(289)	2,773
Net cash used in financing activities	(9,171)	(1,275)	(13,819)	(5,769)
Net cash (used in) provided by operating activities	(3,661)	9,522	6,358	9,493
Effect of foreign currency exchange rate on cash	346	(121)	127	30
Change in cash and cash equivalents	(16,811)	24,068	(5,311)	17,616
Cash and cash equivalents, beginning of period	54,289	51,830	42,789	58,282
Cash and cash equivalents, end of period	$ 37,478	$ 75,898	$ 37,478	$ 75,898