Condensed Consolidated Statements of Cash Flows (Unaudited) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 5,416	$ 9,065
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	2,712	3,218
Share-based compensation expense	1,782	1,373
Excess tax benefits from stock-based awards	(38)	(393)
Loss or (gain) on disposal of assets	1	0
Deferred income tax provision	53	767
Changes in operating assets and liabilities:
Accounts receivable	(966)	1,144
Inventories	438	505
Income taxes receivable	2,738	3,043
Prepaid expenses and other assets	(363)	(264)
Accounts payable	(1,571)	(2,480)
Income taxes payable	520	483
Other current liabilities	320	(661)
Deferred income on shipments to distributors	(2,335)	(667)
Net cash provided by operating activities	8,707	15,133
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of property, plant and equipment	(1,947)	(2,489)
Purchases of investments	(14,401)	(4,708)
Proceeds from sale and maturities of investments	9,100	16,250
Net cash provided by (used) in investing activities	(7,248)	9,053
CASH FLOWS FROM FINANCING ACTIVITIES:
Repayments of debt	0	(2,143)
Proceeds from the issuance of common stock	1,098	9,258
Repurchases of common stock	(6,000)	(5,803)
Payment of cash dividends	(2,452)	(2,163)
Purchase of stock for withholding taxes on vested restricted stock	(80)	(28)
Excess tax benefits from stock-based awards	38	393
Net cash used in financing activities	(7,396)	(486)
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	(5,937)	23,700
CASH AND CASH EQUIVALENTS - Beginning of period	60,610	74,738
CASH AND CASH EQUIVALENTS - End of period	$ 54,673	$ 98,438