Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jul. 05, 2015	Jun. 29, 2014
Cash flows from operating activities:
Net income	$ 64,216	$ 44,454
Adjustments to reconcile net income to net cash provided by operating activities:
Stock-based compensation expense	11,577	7,960
Depreciation of property, plant, and equipment	4,816	4,051
Amortization of intangible assets	2,183	1,830
Amortization of discounts or premiums on investments	377	1,284
Realized gain on sale of investments	(221)	(606)
Tax effect of stock option exercises	(9,358)	(3,481)
Change in deferred income taxes	(2,010)	(1,507)
Accounts receivable	(5,387)	(16,952)
Unbilled revenue	(52,697)	(587)
Inventories	(11,200)	(5,150)
Deferred costs	344	(16,189)
Deferred revenue	8,485	10,516
Accrued income taxes	8,719	2,777
Accrued expenses	(3,887)	(1,537)
Other	(7,312)	4,845
Net cash provided by operating activities	8,645	31,708
Cash flows from investing activities:
Purchases of investments	(222,834)	(189,746)
Maturities and sales of investments	252,768	177,280
Cash paid for purchased technology	(10,475)	0
Purchases of property, plant, and equipment	(9,525)	(5,341)
Net cash provided by (used in) investing activities	9,934	(17,807)
Cash flows from financing activities:
Issuance of common stock under stock option plans	21,457	9,026
Repurchase of common stock	(35,848)	(27,004)
Payment of dividends	(6,110)	0
Tax effect of stock option exercises	9,358	3,481
Net cash used in financing activities	(11,143)	(14,497)
Effect of foreign exchange rate changes on cash and cash equivalents	(1,439)	124
Net change in cash and cash equivalents	5,997	(472)
Cash and cash equivalents at beginning of period	55,694	40,644
Cash and cash equivalents at end of period	61,691	40,172
Noncash items related to discontinued operations:
Depreciation and Amortization, Discontinued Operations	566	576
Capital expenditures	482	261
Stock-based compensation expense	$ 427	$ 555