Condensed Consolidated Statement of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended		12 Months Ended
	Jul. 02, 2021	Jul. 02, 2021	Jul. 03, 2020	Dec. 31, 2020	Dec. 31, 2019
Statement of Cash Flows [Abstract]
Net earnings (loss)	$ 11,856	$ 19,840	$ 185
Earnings from discontinued operations, net of tax	0	0	692
Earnings from continuing operations	11,856	19,840	(507)
Adjustments to reconcile net earnings from continuing operations to net cash (used in) provided by operating activities of continuing operations:
Depreciation and amortization		18,391	19,814
Amortization of debt issuance costs		882	907
Accretion of convertible notes discount		1,484	1,412
Provision for doubtful accounts		290	314
Goodwill, Impairment Loss		0
Gain (Loss) on Disposition of Business	0	234	(493)
Net loss (gain) on sale of assets	5	15	(13)
Net loss on derivative instruments		566	404
Stock compensation expense	2,482	4,225	3,590
Deferred income taxes		2,957	4,124
Changes in assets and liabilities, excluding effects of acquisitions/divestitures:
Accounts receivable		53,232	(11,368)
Increase (Decrease) in Contract with Customer, Asset		(4,637)	(9,158)
Contract costs		(349)	(842)
Inventories		(12,205)	(38,029)
Income tax refunds receivable		1,485	(3,382)
Operating Right-of-Use Assets		781	1,974
Other assets		1,319	135
Accounts payable - trade		(24,068)	(13,872)
Contract liabilities		(18,588)	(11,002)
Operating Lease Liabilities		(919)	(1,916)
Payments for Retention Plans		(25,108)	0
Other current liabilities		(9,470)	528
Income taxes payable		1,532	(2,658)
Pension liabilities		(22,837)	(15,775)
Increase (Decrease) in Other Noncurrent Liabilities		(3,775)	(3,587)
Net cash provided by operating activities		(14,723)	(79,400)
Cash flows from investing activities:
Proceeds from Divestiture of Businesses		0	5,223
Payments for (Proceeds from) Businesses and Interest in Affiliates		(3,428)
Proceeds from Sales of Business, Affiliate and Productive Assets			493
Expenditures for property, plant & equipment		(8,102)	(9,592)
Payments to Acquire Businesses, Net of Cash Acquired		0	(304,661)
Other, net		(671)	(366)
Net cash used in investing activities		(12,201)	(308,903)
Cash flows from financing activities:
Net borrowings under revolving credit agreements		0	201,100
Purchase of treasury shares	(46)	(390)	(14,168)
Dividends paid		(11,106)	(11,144)
Other, net		876	1,399
Net cash provided by (used in) financing activities		(10,620)	177,187
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Excluding Exchange Rate Effect		(37,544)	(211,116)
Effect of exchange rate changes on cash and cash equivalents		(183)	314
Cash and cash equivalents at beginning of period					$ 471,540
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	98,362	98,362		$ 136,089
Cash and cash equivalents and restricted cash at end of period	$ 98,362	$ 98,362	$ 260,738	$ 104,377