CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY - USD ($) shares in Thousands, $ in Thousands	Common Shares	Capital in Excess of Par Value	Accumulated Other Comprehensive Income	Retained Earnings	Treasury Shares	Non-controlling Interest	Total
Balance at the beginning of the period at Dec. 31, 2015	$ 331	$ 2,493,100	$ (47,593)	$ 3,131,134	$ (1,294,262)	$ 11,158	$ 4,293,868
Balance (in shares) at Dec. 31, 2015	330,526
Increase (Decrease) in Equity
Net income (loss)				(694,155)		(990)	(695,145)
Dividends to shareholders ($0.18 per share)				(50,926)			(50,926)
Repurchase of treasury shares					(1,687)		(1,687)
Other comprehensive income (loss), net of tax			35,668			371	36,039
Issuance of common shares for stock options exercised, net of surrender of unexercised stock options		562					562
Issuance of common shares for stock options exercised (in shares)	57
Share-based compensation		24,070					24,070
Other	$ 2	(4,315)				(3,774)	(8,087)
Other (in shares)	2,424
Balance at the end of the period at Sep. 30, 2016	$ 333	2,513,417	(11,925)	2,386,053	(1,295,949)	6,765	3,598,694
Balance (in shares) at Sep. 30, 2016	333,007
Balance at the beginning of the period at Dec. 31, 2016	$ 334	2,521,332	(12,119)	2,033,427	(1,295,949)	7,770	3,254,795
Balance (in shares) at Dec. 31, 2016	333,598
Increase (Decrease) in Equity
Net income (loss)				(430,467)		5,001	(425,466)
Dividends to shareholders ($0.18 per share)				(51,460)			(51,460)
Other comprehensive income (loss), net of tax			27,776			317	28,093
Issuance of common shares for stock options exercised, net of surrender of unexercised stock options	$ 1	8,299					8,300
Issuance of common shares for stock options exercised (in shares)	843
Share-based compensation		25,057					25,057
Equity component of exchangeable debt		116,195					116,195
Capped call transactions		40,250					40,250
Adoption of ASU No. 2016-09		1,943		5,150			7,093
Noncontrolling interest contributions (distributions)						12,728	12,728
Other	$ 1	(7,865)					(7,864)
Other (in shares)	1,109
Balance at the end of the period at Sep. 30, 2017	$ 336	$ 2,624,711	$ 15,657	$ 1,556,650	$ (1,295,949)	$ 25,816	$ 2,927,221
Balance (in shares) at Sep. 30, 2017	335,550