Consolidated Condensed Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 30, 2014	Mar. 31, 2013
Cash flows from operating activities:
Net income	$ 18,506	$ 15,583
Adjustments to reconcile net income to net cash provided by operating activities:
Stock-based compensation expense	4,004	3,298
Depreciation of property, plant, and equipment	1,990	1,828
Amortization of intangible assets	916	961
Amortization of discounts or premiums on investments	896	758
Realized gain on sale of investments	(501)	(31)
Tax effect of stock option exercises	(2,165)	(1,376)
Change in deferred income taxes	127	(1,371)
Change in operating assets and liabilities	(6,312)	(860)
Net cash provided by operating activities	17,461	18,790
Cash flows from investing activities:
Purchases of investments	(124,734)	(76,694)
Maturities and sales of investments	117,753	48,248
Purchases of property, plant, and equipment	(2,685)	(1,908)
Net cash used in investing activities	(9,666)	(30,354)
Cash flows from financing activities:
Issuance of common stock under stock option plans	5,951	9,168
Repurchase of common stock	(14,287)	0
Tax effect of stock option exercises	2,165	1,376
Net cash provided by (used in) financing activities	(6,171)	10,544
Effect of foreign exchange rate changes on cash and cash equivalents	195	(1,383)
Net change in cash and cash equivalents	1,819	(2,403)
Cash and cash equivalents at beginning of period	40,644	45,160
Cash and cash equivalents at end of period	$ 42,463	$ 42,757