CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY - USD ($) shares in Thousands, $ in Thousands	Mandatory Convertible Preferred Shares Preferred Stock	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, 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 common 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, net of surrender of unexercised stock options (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)
Noncontrolling interest contributions (distributions), net							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
Increase (Decrease) in Equity
Adoption of ASU No. 2016-09 | Accounting Standards Update 2016-09			1,943		5,150			7,093
Balance at the beginning 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
Increase (Decrease) in Equity
Net income (loss)					(457,530)		10,426	(447,104)
Dividends to common shareholders ($0.18 per share)					(61,956)			(61,956)
Dividends to preferred shareholders ($1.39 per share)					(7,993)			(7,993)
Common stock issuance		$ 40	301,794					301,834
Common stock issuance (in shares)		40,250
Convertible preferred stock issuance	$ 6		278,352					278,358
Convertible preferred stock issuance (in shares)	5,750
Other comprehensive income (loss), net of tax				(18,300)			(101)	(18,401)
Share-based compensation			20,371					20,371
Adjustment to retained earnings | Accounting Standards Update 2016-01					9,144			9,144
Adjustment to retained earnings | Accounting Standards Update 2016-16					(34,132)			(34,132)
Adjustment to retained earnings								(9,144)
Noncontrolling interest contributions (distributions), net							(4,676)	(4,676)
Less: accrued distribution on redeemable noncontrolling interest in subsidiary					(6,668)			(6,668)
Other		$ 2	(3,724)					(3,722)
Other (in shares)		2,400
Balance at the end of the period at Sep. 30, 2018	$ 6	$ 410	$ 3,387,922	$ (7,115)	$ 864,019	$ (1,314,020)	$ 32,606	$ 2,963,828
Balance (in shares) at Sep. 30, 2018	5,750	410,160