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, 2014	$ 328	$ 2,452,261	$ 77,522	$ 3,573,172	$ (1,194,664)	$ 10,170	$ 4,918,789
Balance (in shares) at Dec. 31, 2014	328,196
Increase (Decrease) in Equity
Net income (loss)				(372,675)		381	(372,294)
Dividends to shareholders				(69,363)			(69,363)
Repurchase of treasury shares					(99,598)		(99,598)
Other comprehensive income (loss), net of tax			(125,115)			(1,461)	(126,576)
Issuance of common shares for stock options exercised, net of surrender of unexercised stock options		1,296					1,296
Issuance of common shares for stock options exercised, net of surrender of unexercised stock options (in shares)	141
Share-based compensation		47,863					47,863
Other	$ 3	(8,320)				2,068	(6,249)
Other (in shares)	2,189
Balance at the end 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)				(1,029,742)		135	(1,029,607)
Dividends to shareholders				(67,965)			(67,965)
Repurchase of treasury shares					(1,687)		(1,687)
Other comprehensive income (loss), net of tax			35,474			251	35,725
Issuance of common shares for stock options exercised, net of surrender of unexercised stock options		967					967
Issuance of common shares for stock options exercised, net of surrender of unexercised stock options (in shares)	102
Share-based compensation		32,000					32,000
Other	$ 3	(4,735)				(3,774)	(8,506)
Other (in shares)	2,970
Balance at the end 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)				(546,811)		6,178	(540,633)
Dividends to shareholders				(68,612)			(68,612)
Repurchase of treasury shares					(18,071)		(18,071)
Other comprehensive income (loss), net of tax			23,304			282	23,586
Issuance of common shares for stock options exercised, net of surrender of unexercised stock options	$ 1	(10,736)					(10,735)
Issuance of common shares for stock options exercised, net of surrender of unexercised stock options (in shares)	842
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
Share-based compensation		31,896					31,896
Issuance to Tesco shareholders	$ 32	178,961					178,993
Issuance to Tesco shareholders (in shares)	32,078
Noncontrolling interest contributions (distributions), net						13,018	13,018
Other	$ 1	(8,212)				(291)	(8,502)
Other (in shares)	992
Balance at the end of the period at Dec. 31, 2017	$ 368	$ 2,791,129	$ 11,185	$ 1,423,154	$ (1,314,020)	$ 26,957	$ 2,938,773
Balance (in shares) at Dec. 31, 2017	367,510