Consolidated Condensed Statements of Cash Flows (Unaudited) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Apr. 01, 2012	Apr. 03, 2011
Cash flows from operating activities:
Net income	$ 14,282	$ 13,636
Adjustments to reconcile net income to net cash provided by operating activities:
Stock-based compensation expense	3,314	2,352
Depreciation of property, plant, and equipment	1,551	1,296
Amortization of intangible assets	1,043	1,079
Amortization of discounts or premiums on investments	1,835	1,462
Realized (gain) loss on sale of investments	(94)	5
Tax effect of stock option exercises	(2,838)	(880)
Change in deferred income taxes	(179)	(472)
Change in operating assets and liabilities	(6,060)	2,310
Net cash provided by operating activities	12,854	20,788
Cash flows from investing activities:
Purchases of investments	(56,721)	(64,270)
Maturities and sales of investments	37,188	40,091
Purchases of property, plant, and equipment	(2,487)	(1,577)
Net cash used in investing activities	(22,020)	(25,756)
Cash flows from financing activities:
Issuance of common stock under stock option plans	13,104	9,517
Payment of dividends	(4,271)	(3,316)
Tax effect of stock option exercises	2,838	880
Net cash provided by financing activities	11,671	7,081
Effect of foreign exchange rate changes on cash	951	1,698
Net change in cash and cash equivalents	3,456	3,811
Cash and cash equivalents at beginning of period	38,103	33,203
Cash and cash equivalents at end of period	$ 41,559	$ 37,014