CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (unaudited) - USD ($) $ in Thousands	3 Months Ended				9 Months Ended		12 Months Ended
	Sep. 27, 2020	Mar. 29, 2020	Sep. 29, 2019	Mar. 31, 2019	Sep. 27, 2020	Sep. 29, 2019	Dec. 31, 2019
Cash Flows from Operating Activities:
Net income/(loss)	$ 83,298	$ 80,236	$ 92,283	$ 73,768	$ 218,524	$ 247,337
Adjustments to reconcile net income to net cash provided by operating activities:
Asset impairment					25,364	6,362
Depreciation, depletion and amortization					186,602	173,085
Gain on adjustment of environmental reserves					0	(10,675)
Share-based compensation expense					6,551	11,800
Equity in earnings of affiliates	(1,939)		(1,799)		(3,230)	(4,240)
Cash dividends from affiliated companies					4,367	4,002
Net (gain)/loss on disposition of assets					(3,298)	3,811
Pension and postretirement plan expense					43,146	21,837
Pension and postretirement plan contributions					(34,795)	(225,535)
Net increase in deferred taxes					10,013	32,370
Change in assets and liabilities, net of effects from acquisitions and foreign currency adjustments:
Trade accounts receivable					(42,102)	(33,574)
Inventories					10,621	(643)
Payable to suppliers					15,708	(7,183)
Prepaid expenses					(1,857)	(533)
Accrued expenses					40,854	29,611
Income taxes payable and other income tax items					(17,466)	(20,407)
Other assets and liabilities					30,499	11,393
Net cash provided by operating activities					489,501	238,818
Cash Flows from Investing Activities:
Purchases of property, plant and equipment					(116,667)	(147,012)
Cost of acquisitions, net of cash acquired					(49,262)	(111,009)
Proceeds from the sale of assets					8,240	2,887
Investment in affiliates and other, net					571	1,494
Net cash used in investing activities					(157,118)	(253,640)
Cash Flows from Financing Activities:
Proceeds from issuance of debt					1,107,127	258,834
Principal repayment of debt					(428,966)	(109,692)
Net change in commercial paper					(250,000)	12,000
Net increase/(decrease) in outstanding checks					8,544	(7,604)
Proceeds from cross-currency swap					14,480	0
Payment of contingent consideration					(3,000)	(5,000)
Cash dividends					(129,446)	(127,169)
Dividends paid to noncontrolling interests					0	(214)
Shares repurchased					(7,335)	(8,697)
Net cash provided by financing activities					311,404	12,458
Effects of Exchange Rate Changes on Cash					(6,391)	(2,172)
Net Increase/(Decrease) in Cash and Cash Equivalents					637,396	(4,536)
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	$ 782,679		$ 115,853		$ 782,679	$ 115,853	$ 145,283