Consolidated Condensed Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 28, 2014	Sep. 29, 2013
Cash flows from operating activities:
Net income	$ 94,854	$ 53,130
Adjustments to reconcile net income to net cash provided by operating activities:
Stock-based compensation expense	11,258	8,299
Depreciation of property, plant, and equipment	6,194	5,389
Amortization of intangible assets	2,934	2,880
Amortization of discounts or premiums on investments	1,596	1,996
Realized gain on sale of investments	(651)	(103)
Net unrealized loss on trading securities	0	(267)
Tax effect of stock option exercises	(7,178)	(6,584)
Change in deferred income taxes	(2,959)	216
Accounts receivable	(51,961)	(7,010)
Unbilled revenue	(12,234)	(1,862)
Inventories	(6,555)	(1,342)
Deferred revenue	9,453	(1,143)
Accrued income taxes	7,331	5,651
Accrued expenses	6,221	2,486
Other	4,684	(3,035)
Net cash provided by operating activities	62,987	59,235
Cash flows from investing activities:
Purchases of investments	(283,982)	(251,033)
Maturities and sales of investments	239,396	178,372
Purchases of property, plant, and equipment	(9,078)	(6,152)
Net cash used in investing activities	(53,664)	(78,813)
Cash flows from financing activities:
Issuance of common stock under stock option plans	15,651	25,990
Repurchase of common stock	(35,140)	(28,059)
Tax effect of stock option exercises	7,178	6,584
Net cash provided by (used in) financing activities	(12,311)	4,515
Effect of foreign exchange rate changes on cash and cash equivalents	523	349
Net change in cash and cash equivalents	(2,465)	(14,714)
Cash and cash equivalents at beginning of period	40,644	45,160
Cash and cash equivalents at end of period	$ 38,179	$ 30,446