CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Apr. 01, 2018	Apr. 02, 2017
Cash flows from operating activities:
Net income	$ 86,974	$ 85,221
Adjustments to reconcile net income to net cash used for operating activities:
Depreciation	16,336	16,143
Amortization	9,204	11,070
Stock-based compensation	9,544	8,945
Provision for excess and obsolete inventory	3,522	2,726
Deferred taxes	8,696	(3,477)
Contingent consideration adjustment	(4,968)	634
Other	1,393	2
Changes in operating assets and liabilities, net of business acquired:
Accounts receivable	(140,747)	(123,792)
Inventories	(21,017)	(62,152)
Prepayments and other assets	(679)	1,104
Accounts payable and other accrued expenses	(46,706)	(7,553)
Deferred revenue and customer advances	9,644	(3,333)
Retirement plans contributions	(1,020)	(947)
Income taxes	(12,106)	14,288
Net cash used for operating activities	(81,930)	(61,121)
Cash flows from investing activities:
Purchases of property, plant and equipment	(34,797)	(22,066)
Purchases of marketable securities	(490,324)	(153,317)
Proceeds from sales of marketable securities	800,671	213,593
Proceeds from maturities of marketable securities	212,698	88,184
Acquisition of business, net of cash acquired	(25,356)
Net cash provided by investing activities	462,892	126,394
Cash flows from financing activities:
Issuance of common stock under stock purchase and stock option plans	10,654	15,084
Repurchase of common stock	(134,276)	(37,730)
Payments related to net settlement of employee stock compensation awards	(19,629)	(12,289)
Dividend payments	(17,588)	(14,021)
Payments of contingent consideration	(13,571)	(1,050)
Net cash used for financing activities	(174,410)	(50,006)
Effects of exchange rate changes on cash and cash equivalents	1,478	1,595
Increase in cash and cash equivalents	208,030	16,862
Cash and cash equivalents at beginning of period	429,843	307,884
Cash and cash equivalents at end of period	$ 637,873	$ 324,746