Condensed Consolidated Statements of Cash Flows (Unaudited) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 5,245	$ 5,907
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	3,404	2,712
Share-based compensation expense	1,619	1,782
Excess tax benefits from stock-based awards	(89)	(38)
Loss on disposal of assets	0	1
Deferred income tax provision	(833)	(438)
Changes in operating assets and liabilities
Accounts receivable	(3,757)	(966)
Inventories	466	438
Income taxes receivable	1,244	2,738
Prepaid expenses and other assets	(536)	(363)
Accounts payable	(3,817)	(1,571)
Income taxes payable	583	520
Other current liabilities	1,653	320
Deferred income on shipments to distributors	2,544	(2,335)
Net cash provided by operating activities	7,726	8,707
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of property, plant and equipment	(1,551)	(1,947)
Purchases of investments	(9,037)	(14,401)
Proceeds from sale and maturities of investments	29,500	9,100
Change in restricted cash	102	0
Net cash provided by (used in) investing activities	19,014	(7,248)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from the issuance of common stock	1,508	1,098
Repurchases of common stock	0	(6,000)
Payment of cash dividends	0	(2,452)
Purchase of stock for withholding taxes on vested restricted stock	(134)	(80)
Excess tax benefits from stock-based awards	89	38
Net cash provided by (used in) financing activities	1,463	(7,396)
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	28,203	(5,937)
CASH AND CASH EQUIVALENTS - Beginning of period	27,281	60,610
CASH AND CASH EQUIVALENTS - End of period	$ 55,484	$ 54,673