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)				(582,944)		(2,175)	(585,119)
Dividends to shareholders				(33,925)			(33,925)
Repurchase of treasury shares					(1,687)		(1,687)
Other comprehensive income (loss), net of tax			39,343			461	39,804
Issuance of common shares for stock options exercised, net of surrender of unexercised stock options		39					39
Issuance of common shares for stock options exercised (in shares)	4
Share-based compensation		16,596					16,596
Other	$ 2	(4,284)				(2,596)	(6,878)
Other (in shares)	2,524
Balance at the end of the period at Jun. 30, 2016	$ 333	2,505,451	(8,250)	2,514,265	(1,295,949)	6,848	3,722,698
Balance (in shares) at Jun. 30, 2016	333,054
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)				(281,935)		2,888	(279,047)
Dividends to shareholders				(34,307)			(34,307)
Other comprehensive income (loss), net of tax			16,913			157	17,070
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		18,045					18,045
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 contribution						13,018	13,018
Other	$ 1	(7,845)				(290)	(8,134)
Other (in shares)	1,058
Balance at the end of the period at Jun. 30, 2017	$ 336	$ 2,617,719	$ 4,794	$ 1,722,335	$ (1,295,949)	$ 23,543	$ 3,072,778
Balance (in shares) at Jun. 30, 2017	335,499