Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Statement of Cash Flows [Abstract]
Cash and cash equivalents at beginning of year	$ 746,724	$ 613,110
Cash flows from operating activities:
Net income	117,698	123,635
Adjustments to reconcile net income to cash flows from operating activities:
Depreciation and amortization	62,260	53,694
Stock-based compensation and other	2,560	2,501
Equity in net income of unconsolidated investments (net of tax)	(16,511)	(26,604)
Dividends received from unconsolidated investments and nonmarketable securities	4,950	0
Pension and postretirement benefit	(4,226)	(1,719)
Pension and postretirement contributions	(15,329)	(6,113)
Unrealized gain on investments in marketable securities	(1,762)	(627)
Loss on early extinguishment of debt	27,798	0
Deferred income taxes	(19,384)	4,790
Working capital changes	(49,185)	17,730
Non-cash transfer of 40% value of construction in progress of Kemerton plant to MRL	43,223	36,723
Other, net	5,857	(48,956)
Net cash provided by operating activities	157,949	155,054
Cash flows from investing activities:
Acquisitions, net of cash acquired	0	(22,572)
Capital expenditures	(179,683)	(214,529)
Sales of marketable securities, net	5,245	2,589
Investments in equity and other corporate investments	(286)	(356)
Net cash used in investing activities	(174,724)	(234,868)
Cash flows from financing activities:
Proceeds from issuance of common stock	1,453,888	0
Repayments of long-term debt and credit agreements	(1,174,980)	0
Proceeds from borrowings of credit agreements	0	250,000
-325159000	(325,159)	(151,872)
Fees related to early extinguishment of debt	(23,719)	0
Dividends paid to shareholders	(41,130)	(38,982)
Dividends paid to noncontrolling interests	(26,219)	(14,286)
Proceeds from exercise of stock options	1,183	10,195
Withholding taxes paid on stock-based compensation award distributions	(6,860)	(3,825)
Other	(253)	(214)
Net cash (used in) provided by financing activities	(143,249)	51,016
Net effect of foreign exchange on cash and cash equivalents	(16,841)	(31,084)
Decrease in cash and cash equivalents	(176,865)	(59,882)
Cash and cash equivalents at end of period	$ 569,859	$ 553,228