Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jul. 02, 2017	Jul. 03, 2016
Cash flows from operating activities:
Net income	$ 101,727	$ 57,644
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	15,329	11,261
Depreciation of property, plant, and equipment	6,288	5,577
Amortization of intangible assets	1,740	1,862
Amortization of discounts or premiums on investments	171	204
Realized (gain) loss on sale of investments	(107)	(128)
Revaluation of contingent consideration	(151)	(463)
Change in deferred income taxes	2,998	(2,943)
Accounts receivable	(18,841)	(17,737)
Unbilled revenue	(3,315)	(25,507)
Inventories	(7,711)	11,964
Prepaid expenses and other current assets	(27,717)	(7,449)
Accounts payable	11,814	6,224
Accrued expenses	(157)	1,762
Accrued income taxes	(566)	2,245
Deferred revenue and customer deposits	9,110	3,998
Other	8	542
Net cash provided by operating activities	90,620	49,311
Cash flows from investing activities:
Purchases of investments	(304,611)	(455,915)
Maturities and sales of investments	279,654	427,196
Purchases of property, plant, and equipment	(12,172)	(5,347)
Cash paid for acquisition of businesses, net of cash acquired	(25,519)	0
Net cash provided by (used in) investing activities	(291)	(113)
Net cash provided by (used in) investing activities	(62,939)	(34,179)
Cash flows from financing activities:
Issuance of common stock under stock plans	35,050	8,700
Repurchase of common stock	(62,343)	(8,718)
Payment of dividends	(13,864)	(12,335)
Payment of contingent consideration	0	(337)
Net cash provided by (used in) financing activities	(41,157)	(12,690)
Effect of foreign exchange rate changes on cash and cash equivalents	2,101	512
Net change in cash and cash equivalents	(11,375)	2,954
Cash and cash equivalents at beginning of period	79,641	51,975
Cash and cash equivalents at end of period	$ 68,266	$ 54,929