CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY - USD ($) $ 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)				(398,294)		724	(397,570)
Dividends to shareholders				(16,922)			(16,922)
Repurchase of treasury shares					(1,687)		(1,687)
Other comprehensive income (loss), net of tax			34,329			419	34,748
Share-based compensation		7,374					7,374
Other	$ 1	(3,191)				(424)	(3,614)
Other (in shares)	1,149
Balance at the end of the period at Mar. 31, 2016	$ 332	2,497,283	(13,264)	2,715,918	(1,295,949)	11,877	3,916,197
Balance (in shares) at Mar. 31, 2016	331,675
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)				(148,984)		917	(148,067)
Dividends to shareholders				(17,153)			(17,153)
Other comprehensive income (loss), net of tax			783			49	832
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		10,280					10,280
Equity component of exchangeable debt		116,195					116,195
Purchase of capped call hedge transactions		(40,250)					(40,250)
Adoption of ASU No. 2016-09		1,943		5,150			7,093
Other	$ 1	(5,342)				(290)	(5,631)
Other (in shares)	1,126
Balance at the end of the period at Mar. 31, 2017	$ 336	$ 2,612,457	$ (11,336)	$ 1,872,440	$ (1,295,949)	$ 8,446	$ 3,186,394
Balance (in shares) at Mar. 31, 2017	335,567