Consolidated Condensed Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 29, 2014	Jun. 30, 2013
Cash flows from operating activities:
Net income	$ 44,454	$ 32,403
Adjustments to reconcile net income to net cash provided by operating activities:
Stock-based compensation expense	7,960	6,079
Depreciation of property, plant, and equipment	4,051	3,596
Amortization of intangible assets	1,830	1,921
Amortization of discounts or premiums on investments	1,284	1,443
Realized gain on sale of investments	(606)	(83)
Net unrealized loss on trading securities	0	462
Tax effect of stock option exercises	(3,481)	(2,773)
Change in deferred income taxes	(1,507)	(1,748)
Accounts receivable	(16,952)	(3,897)
Inventories	(5,150)	(821)
Deferred costs	(16,189)	(384)
Deferred revenue	10,516	(96)
Other	5,498	2,873
Net cash provided by operating activities	31,708	38,975
Cash flows from investing activities:
Purchases of investments	(189,746)	(167,652)
Maturities and sales of investments	177,280	129,329
Purchases of property, plant, and equipment	(5,341)	(4,310)
Net cash used in investing activities	(17,807)	(42,633)
Cash flows from financing activities:
Issuance of common stock under stock option plans	9,026	16,242
Repurchase of common stock	(27,004)	(11,891)
Tax effect of stock option exercises	3,481	2,773
Net cash provided by (used in) financing activities	(14,497)	7,124
Effect of foreign exchange rate changes on cash and cash equivalents	124	(752)
Net change in cash and cash equivalents	(472)	2,714
Cash and cash equivalents at beginning of period	40,644	45,160
Cash and cash equivalents at end of period	$ 40,172	$ 47,874