Consolidated Condensed Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 29, 2013	Sep. 30, 2012
Cash flows from operating activities:
Net income	$ 53,130	$ 51,854
Adjustments to reconcile net income to net cash provided by operating activities:
Stock-based compensation expense	8,299	6,795
Depreciation of property, plant, and equipment	5,389	4,977
Amortization of intangible assets	2,880	3,124
Amortization of discounts or premiums on investments	1,996	4,719
Realized gain on sale of investments	(103)	(1,411)
Tax effect of stock option exercises	(6,584)	(3,256)
Change in deferred income taxes	216	(1,509)
Net unrealized loss on trading securities	267
Change in operating assets and liabilities	(6,255)	9,516
Net cash provided by operating activities	59,235	74,809
Cash flows from investing activities:
Purchases of investments	(251,033)	(355,351)
Maturities and sales of investments	178,372	309,081
Purchases of property, plant, and equipment	(6,152)	(7,621)
Net cash used in investing activities	(78,813)	(53,891)
Cash flows from financing activities:
Issuance of common stock under stock option plans	25,990	15,579
Repurchase of common stock	(28,059)
Payment of dividends		(13,706)
Tax effect of stock option exercises	6,584	3,256
Net cash provided by financing activities	4,515	5,129
Effect of foreign exchange rate changes on cash and cash equivalents	349	(9,992)
Net change in cash and cash equivalents	(14,714)	16,055
Cash and cash equivalents at beginning of period	45,160	38,103
Cash and cash equivalents at end of period	$ 30,446	$ 54,158