CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (unaudited) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended		12 Months Ended
	Jun. 28, 2020	Mar. 29, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 28, 2020	Jun. 30, 2019	Dec. 31, 2019
Cash Flows from Operating Activities:
Net income/(loss):	$ 54,990	$ 80,236	$ 81,286	$ 73,768	$ 135,226	$ 155,054
Adjustments to reconcile net income to net cash provided by operating activities:
Asset impairment					8,759	7,284
Depreciation, depletion and amortization					123,447	116,978
Share-based compensation expense					1,936	8,866
Equity in earnings of affiliates	(778)		(1,511)		(1,291)	(2,441)
Cash dividends from affiliated companies					3,276	3,297
Net (gain)/loss on disposition of assets					(2,265)	3,943
Pension and postretirement plan expense					29,135	13,647
Pension and postretirement plan contributions					(31,105)	(213,579)
Net increase in deferred taxes					19,653	37,953
Change in assets and liabilities, net of effects from acquisitions and foreign currency adjustments:
Trade accounts receivable					(13,516)	(46,191)
Inventories					(31,984)	(16,825)
Payable to suppliers					17,844	(2,842)
Prepaid expenses					(8,769)	(4,976)
Accrued expenses					9,261	(7,741)
Income taxes payable and other income tax items					8,533	(26,990)
Other assets and liabilities					13,851	14,644
Net cash provided by operating activities					281,991	40,081
Cash Flows from Investing Activities:
Purchases of property, plant and equipment					(76,417)	(102,272)
Cost of acquisitions, net of cash acquired					(3,787)	(455)
Proceeds from the sale of assets					4,845	1,498
Investment in affiliates and other, net					524	1,301
Net cash used in investing activities					(74,835)	(99,928)
Cash Flows from Financing Activities:
Proceeds from issuance of debt					1,105,139	243,394
Principal repayment of debt					(269,970)	(81,025)
Net change in commercial paper					(250,000)	(18,000)
Net increase/(decrease) in outstanding checks					7,469	(11,697)
Proceeds from cross-currency swap					14,480	0
Payment of contingent consideration					(2,500)	(5,000)
Cash dividends					(86,337)	(84,160)
Dividends paid to noncontrolling interests					0	(214)
Shares repurchased					(3,950)	(8,550)
Net cash provided by financing activities					514,331	34,748
Effects of Exchange Rate Changes on Cash					(9,498)	1,005
Net Increase/(Decrease) in Cash and Cash Equivalents					711,989	(24,094)
Cash and cash equivalents at beginning of period		$ 145,283		$ 120,389	145,283	120,389	$ 120,389
Cash and cash equivalents at end of period	$ 857,272		$ 96,295		$ 857,272	$ 96,295	$ 145,283