Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Oct. 01, 2017	Oct. 02, 2016
Cash flows from operating activities:
Net income	$ 204,075	$ 111,319
Adjustments to reconcile net income to net cash provided by operating activities:
(Gain) loss on sale of discontinued business	0	255
Stock-based compensation expense	23,355	15,883
Depreciation of property, plant, and equipment	9,811	8,551
Amortization of intangible assets	2,539	2,581
Amortization of discounts or premiums on investments	188	288
Realized (gain) loss on sale of investments	(370)	(733)
Revaluation of contingent consideration	88	(463)
Change in deferred income taxes	(1,830)	(1,415)
Accounts receivable	(58,379)	(37,802)
Unbilled revenue	(46,010)	(9,986)
Inventories	(18,550)	10,780
Prepaid expenses and other current assets	(14,968)	(4,524)
Accounts payable	19,132	2,089
Accrued expenses	8,819	7,560
Accrued income taxes	3,233	(531)
Deferred revenue and customer deposits	7,060	4,071
Other	1,861	(1,265)
Net cash provided by operating activities	140,054	106,658
Cash flows from investing activities:
Purchases of investments	(415,508)	(598,955)
Maturities and sales of investments	428,076	529,207
Purchases of property, plant, and equipment	(20,044)	(10,491)
Cash paid for acquisition of businesses, net of cash acquired	(24,118)	(2,483)
Net cash provided by (used in) investing activities	(291)	(113)
Net cash provided by (used in) investing activities	(31,885)	(82,835)
Cash flows from financing activities:
Issuance of common stock under stock plans	44,750	23,091
Repurchase of common stock	(99,347)	(18,941)
Payment of dividends	(21,236)	(18,761)
Payment of contingent consideration	(1,926)	(337)
Net cash provided by (used in) financing activities	(77,759)	(14,948)
Effect of foreign exchange rate changes on cash and cash equivalents	1,298	295
Net change in cash and cash equivalents	31,708	9,170
Cash and cash equivalents at beginning of period	79,641	51,975
Cash and cash equivalents at end of period	$ 111,349	$ 61,145