Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Statement of Cash Flows [Abstract]
Cash and cash equivalents at beginning of year	$ 613,110	$ 555,320
Cash flows from operating activities:
Net income	123,635	151,526
Adjustments to reconcile net income to cash flows from operating activities:
Depreciation and amortization	53,694	49,283
Gain on sale of property	0	(11,079)
Stock-based compensation and other	2,501	5,556
Equity in net income of unconsolidated investments (net of tax)	(26,604)	(35,181)
Dividends received from unconsolidated investments and nonmarketable securities	0	3,034
Pension and postretirement (benefit) expense	(1,719)	578
Pension and postretirement contributions	(6,113)	(3,555)
Unrealized gain on investments in marketable securities	(627)	(476)
Deferred income taxes	4,790	7,580
Working capital changes	17,730	(122,939)
Other, net	(12,233)	10,589
Net cash provided by operating activities	155,054	54,916
Cash flows from investing activities:
Acquisitions, net of cash acquired	(22,572)	0
Capital expenditures	(214,529)	(216,132)
Proceeds from sale of property and equipment	0	10,356
Sales of marketable securities, net	2,589	1,090
Investments in equity and other corporate investments	(356)	(2,509)
Net cash used in investing activities	(234,868)	(207,195)
Cash flows from financing activities:
Proceeds from borrowings of credit agreements	250,000	0
Other (repayments) borrowings, net	151,872	(118,223)
Dividends paid to shareholders	(38,982)	(35,387)
Dividends paid to noncontrolling interests	(14,286)	0
Proceeds from exercise of stock options	10,195	2,676
Withholding taxes paid on stock-based compensation award distributions	(3,825)	(10,255)
Debt financing costs	214	0
Net cash provided by financing activities	51,016	75,257
Net effect of foreign exchange on cash and cash equivalents	(31,084)	(13,024)
Decrease in cash and cash equivalents	(59,882)	(90,046)
Cash and cash equivalents at end of period	$ 553,228	$ 465,274