CONDENSED CONSOLIDATED STATEMENTS OF EQUITY (Unaudited) - USD ($) $ in Thousands	Total	Common Stock Issued	Common Stock Treasury	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Loss	Noncontrolling Interests
Beginning balance at Dec. 31, 2018	$ 313,376	$ 141,842	$ (795,821)	$ 190,597	$ 1,298,752	$ (567,107)	$ 45,113
Increase (Decrease) in Stockholders' Equity
Net income (loss)	22,537				20,697		1,840
Sale of subsidiary shares to noncontrolling interest	876						876
Total other comprehensive income	4,531					4,111	420
Stock appreciation rights exercised, net	(8)	2	(8)	(2)
Vesting of restricted stock units and other stock grants, net	(1,456)	198	(1,456)	(198)
Vesting of performance share units, net	(8,248)	1,136	(8,235)	(1,149)
Amortization of unearned portion of stock-based compensation, net of forfeitures	3,664			3,664
Ending balance at Mar. 31, 2019	335,272	143,178	(805,520)	192,912	1,340,878	(584,425)	48,249
Beginning balance at Dec. 31, 2018	313,376	141,842	(795,821)	190,597	1,298,752	(567,107)	45,113
Increase (Decrease) in Stockholders' Equity
Net income (loss)	471,323
Total other comprehensive income	(1,091)
Ending balance at Sep. 30, 2019	751,260	143,396	(832,775)	198,007	1,784,871	(587,759)	45,520
Beginning balance at Mar. 31, 2019	335,272	143,178	(805,520)	192,912	1,340,878	(584,425)	48,249
Increase (Decrease) in Stockholders' Equity
Net income (loss)	10,929				8,642		2,287
Total other comprehensive income	3,598					4,196	(598)
Stock appreciation rights exercised, net	(108)	18	(108)	(18)
Vesting of performance share units, net	(1,375)	198	(1,375)	(198)
Amortization of unearned portion of stock-based compensation, net of forfeitures	2,338			2,338
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders	4,690						4,690
Noncontrolling Interest, Increase from Subsidiary Equity Issuance	3,150						3,150
Ending balance at Jun. 30, 2019	349,114	143,394	(807,003)	195,034	1,349,520	(580,229)	48,398
Increase (Decrease) in Stockholders' Equity
Net income (loss)	437,857				435,351		2,506
Total other comprehensive income	(9,220)					(7,530)	(1,690)
Strategic venture exit	(3,694)						(3,694)
Stock appreciation rights exercised, net	(1)		(1)
Vesting of restricted stock units and other stock grants, net	(19)	2	(19)	(2)
Treasury shares repurchased	(25,752)		(25,752)
Amortization of unearned portion of stock-based compensation, net of forfeitures	2,975			2,975
Ending balance at Sep. 30, 2019	751,260	143,396	(832,775)	198,007	1,784,871	(587,759)	45,520
Beginning balance at Dec. 31, 2019	789,659	143,400	(838,893)	200,595	1,824,100	(587,622)	48,079
Increase (Decrease) in Stockholders' Equity
Net income (loss)	1,227				141		1,086
Total other comprehensive income	(30,002)					(28,854)	(1,148)
Vesting of restricted stock units and other stock grants, net	(889)	230	(889)	(230)
Vesting of performance share units, net	(3,205)	589	(3,205)	(589)
Amortization of unearned portion of stock-based compensation, net of forfeitures	2,080			2,080
Ending balance at Mar. 31, 2020	758,870	144,219	(842,987)	201,856	1,824,241	(616,476)	48,017
Beginning balance at Dec. 31, 2019	789,659	143,400	(838,893)	200,595	1,824,100	(587,622)	48,079
Increase (Decrease) in Stockholders' Equity
Net income (loss)	(16,567)
Total other comprehensive income	(8,851)
Ending balance at Sep. 30, 2020	766,414	144,268	(843,098)	206,113	1,804,061	(597,052)	52,122
Beginning balance at Mar. 31, 2020	758,870	144,219	(842,987)	201,856	1,824,241	(616,476)	48,017
Increase (Decrease) in Stockholders' Equity
Net income (loss)	(9,455)				(10,602)		1,147
Total other comprehensive income	13,031					12,858	173
Stock appreciation rights exercised, net	(16)	8	(16)	(8)
Vesting of restricted stock units and other stock grants, net	0	18		(18)
Amortization of unearned portion of stock-based compensation, net of forfeitures	2,086			2,086
Ending balance at Jun. 30, 2020	764,516	144,245	(843,003)	203,916	1,813,639	(603,618)	49,337
Increase (Decrease) in Stockholders' Equity
Net income (loss)	(8,339)				(9,578)		1,239
Total other comprehensive income	8,120					6,566	1,554
Stock appreciation rights exercised, net	(8)	3	(8)	(3)
Vesting of restricted stock units and other stock grants, net	(87)	20	(87)	(20)
Amortization of unearned portion of stock-based compensation, net of forfeitures	2,220			2,220
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders	8						8
Ending balance at Sep. 30, 2020	$ 766,414	$ 144,268	$ (843,098)	$ 206,113	$ 1,804,061	$ (597,052)	$ 52,122