Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 34,016	$ 50,708	$ 16,294
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	11,178	13,091	15,684
Share-based compensation	5,854	4,725	3,964
Excess tax benefits from stock-based awards	(477)	(211)	0
Equipment impairment	0	0	6,514
Loss or (gain) on disposal of assets	(13)	11	(173)
Accrued rent	0	0	(272)
Deferred income tax provision (benefit)	3,104	(7,366)	(2,159)
Changes in operating assets and liabilities:
Accounts receivable	8,746	(7,801)	(5,687)
Inventories	455	(2,522)	3,292
Income taxes receivable	(334)	(2,536)	2,772
Prepaid expenses and other assets	(165)	(2,294)	392
Accounts payable	(2,576)	4,367	(530)
Accrued compensation	(3,454)	5,632	(4,263)
Accrued commissions	(103)	410	(709)
Income taxes payable	919	1,261	212
Other accrued liabilities	913	171	36
Deferred income on shipments to distributors	(7,975)	15,241	2,269
Net cash provided by operating activities	50,088	72,887	37,636
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of property, plant and equipment	(7,277)	(9,760)	(12,133)
Purchases of investments	(77,510)	(34,589)	(29,210)
Proceeds from sales and maturities of investments	40,585	1,500	55,776
Net cash provided (used) in investing activities	(44,202)	(42,849)	14,433
CASH FLOWS FROM FINANCING ACTIVITIES:
Long-term debt borrowings	0	0	15,000
Repayments of debt	(2,857)	(8,571)	(3,572)
Proceeds from the issuance of common stock	12,040	6,861	394
Repurchase of common stock	(20,253)	(16,053)	(32,448)
Payments of cash dividends	(9,358)	(8,646)	(8,888)
Purchase of stock for withholding taxes on vested restricted stock	(63)	0	0
Excess tax benefits from stock-based awards	477	211	0
Net cash used in financing activities	(20,014)	(26,198)	(29,514)
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	(14,128)	3,840	22,555
CASH AND CASH EQUIVALENTS--Beginning of year	74,738	70,898	48,343
CASH AND CASH EQUIVALENTS--End of year	60,610	74,738	70,898
SUPPLEMENTAL DISCLOSURE OF CASH FLOW INFORMATION:
Interest	19	223	272
Income taxes	$ 11,164	$ 33,125	$ 7,481