Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Apr. 01, 2017
Operating activities
Net income	$ 36,029	$ 38,891
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	11,614	9,128
Amortization of intangibles	11,998	5,944
Provision for bad debts	(13)	351
Non-cash inventory charges	17,896
Unrealized gain on investments	(1,864)
Loss on sale of property, plant, and equipment	99	600
Stock-based compensation	8,714	3,583
Deferred income taxes	842	616
Changes in operating assets and liabilities:
Accounts receivable	(8,417)	(11,267)
Inventories	(269)	(3,296)
Accounts payable	2,990	(3,295)
Accrued expenses (including post-retirement)	12,573	4,140
Accrued payroll and severance	(18,607)	(20,221)
Accrued taxes	(1,174)	(220)
Prepaid expenses and other	(3,143)	(2,011)
Net cash provided by operating activities	69,268	22,943
Investing activities
Acquisitions of businesses, net of cash acquired	(306,487)	(14,172)
Proceeds from maturities of short-term investments		3,739
Decrease in entrusted loan		655
Purchases of property, plant, and equipment	(17,909)	(12,377)
Proceeds from sale of property, plant, and equipment	19	57
Net cash used in investing activities	(324,377)	(22,098)
Financing activities:
Proceeds of revolving credit facility	50,000
Proceeds of term loan	75,000
Proceeds of senior notes payable	175,000	125,000
Payments of term loan	(2,500)	(1,563)
Payments of revolving credit facility	(47,000)	(112,500)
Net (payments) proceeds related to stock-based award activities	116	(199)
Proceeds (payments) from entrusted loan		(655)
Debt issuance costs	(878)	(71)
Cash dividends paid	(9,198)	(7,472)
Net cash provided by financing activities	240,308	2,938
Effect of exchange rate changes on cash and cash equivalents	(2,417)	(928)
Increase (decrease) in cash and cash equivalents	(17,218)	2,855
Cash and cash equivalents at beginning of year	429,676	275,124
Cash and cash equivalents at end of year	$ 412,458	$ 277,979