Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Apr. 02, 2017	Apr. 03, 2016
Cash flows from operating activities:
Net income	$ 45,655	$ 14,885
Adjustments to reconcile net income to net cash provided by operating activities:
Stock-based compensation expense	7,483	6,804
Depreciation of property, plant, and equipment	3,083	2,757
Amortization of intangible assets	872	1,045
Amortization of discounts or premiums on investments	86	125
Realized (gain) loss on sale of investments	(65)	13
Revaluation of contingent consideration	(275)	(263)
Change in deferred income taxes	921	(2,064)
Accounts receivable	(2,238)	(1,025)
Unbilled revenue	953	4
Inventories	(5,386)	2,646
Prepaid expenses and other current assets	(12,326)	3,221
Accounts payable	7,167	2,216
Accrued expenses	(3,398)	(3,353)
Accrued income taxes	423	467
Deferred revenue and customer deposits	5,494	(155)
Other	(734)	257
Net cash provided by operating activities	47,715	27,580
Cash flows from investing activities:
Purchases of investments	(193,612)	(219,616)
Maturities and sales of investments	171,667	223,334
Purchases of property, plant, and equipment	(6,095)	(2,237)
Cash paid for acquisition of business	(176)	0
Cash paid related to discontinued business	(291)	0
Net cash provided by (used in) investing activities	(28,507)	1,481
Cash flows from financing activities:
Issuance of common stock under stock plans	29,139	3,440
Repurchase of common stock	(30,067)	0
Payment of dividends	(6,497)	(5,950)
Net cash provided by (used in) financing activities	(7,425)	(2,510)
Effect of foreign exchange rate changes on cash and cash equivalents	1,004	1,388
Net change in cash and cash equivalents	12,787	27,939
Cash and cash equivalents at beginning of period	79,641	51,975
Cash and cash equivalents at end of period	$ 92,428	$ 79,914