Consolidated Condensed Statements of Cash Flows (Unaudited) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2012	Oct. 02, 2011
Cash flows from operating activities:
Net income	$ 51,854	$ 50,770
Adjustments to reconcile net income to net cash provided by operating activities:
Stock-based compensation expense	6,795	5,829
Depreciation of property, plant, and equipment	4,977	4,082
Amortization of intangible assets	3,124	3,181
Amortization of discounts or premiums on investments	4,719	4,675
Realized gain on sale of investments	(1,411)	(33)
Tax effect of stock option exercises	(3,256)	(3,624)
Change in deferred income taxes	(1,509)	(359)
Change in operating assets and liabilities	9,516	(2,184)
Net cash provided by operating activities	74,809	62,337
Cash flows from investing activities:
Purchases of investments	(355,351)	(288,045)
Maturities and sales of investments	309,081	217,528
Purchases of property, plant, and equipment	(7,621)	(5,545)
Net cash used in investing activities	(53,891)	(76,062)
Cash flows from financing activities:
Issuance of common stock under stock option plans	15,579	27,837
Repurchase of common stock		(10,000)
Payment of dividends	(13,706)	(10,897)
Tax effect of stock option exercises	3,256	3,624
Net cash provided by financing activities	5,129	10,564
Effect of foreign exchange rate changes on cash and cash equivalents	(9,992)	133
Net change in cash and cash equivalents	16,055	(3,028)
Cash and cash equivalents at beginning of period	38,103	33,203
Cash and cash equivalents at end of period	$ 54,158	$ 30,175