CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid in Capital	Retained Earnings	Accumulated Other Comprehensive Income (loss)	Treasury Stock	Non- controlling Interest
Beginning Balance (in shares) at Dec. 31, 2014		43,420				1,981
Beginning Balance at Dec. 31, 2014	$ 1,913,699	$ 43,420	$ 422,394	$ 1,827,845	$ (260,895)	$ (121,455)	$ 2,390
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	245,713			244,863			850
Cash dividends ($1.36 per share)	(56,532)			(56,532)
Other comprehensive loss	(110,305)				(110,229)		(76)
Distributions to noncontrolling interest shareholders	(1,343)						(1,343)
Settlement of convertible notes (in shares)						(2)
Settlement of convertible notes	5		(128)			$ 133
Settlement of note hedges associated with convertible notes (in shares)						2
Settlement of note hedges associated with convertible notes and warrants	1		270			$ (269)
Shares issued under compensation plans (in shares)		97				(70)
Shares issued under compensation plans	19,782	$ 97	17,591			$ 2,094
Deferred compensation (in shares)						(3)
Deferred compensation	73					$ 73
Ending Balance (in shares) at Dec. 31, 2015		43,517				1,908
Ending Balance at Dec. 31, 2015	2,011,093	$ 43,517	440,127	2,016,176	(371,124)	$ (119,424)	1,821
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	237,841			237,377			464
Cash dividends ($1.36 per share)	(58,960)			(58,960)
Other comprehensive loss	(66,804)				(66,761)		(43)
Distributions to noncontrolling interest shareholders	(464)						(464)
Acquisition of noncontrolling interest	(9,231)		(6,621)		(832)		(1,778)
Settlement of convertible notes (in shares)		2,168				(430)
Settlement of convertible notes	3,296	$ 2,168	(32,004)			$ 33,132
Settlement of note hedges associated with convertible notes (in shares)						316
Settlement of note hedges associated with convertible notes and warrants	2		86,048			$ (86,046)
Reclassification of convertible notes to mezzanine equity	(1,824)		(1,824)
Shares issued under compensation plans (in shares)		129				(51)
Shares issued under compensation plans	22,492	$ 129	21,074			$ 1,289
Deferred compensation (in shares)						(2)
Deferred compensation	76					$ 76
Ending Balance (in shares) at Dec. 31, 2016		45,814				1,741
Ending Balance at Dec. 31, 2016	2,137,517	$ 45,814	506,800	2,194,593	(438,717)	$ (170,973)	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	152,530			152,530
Cash dividends ($1.36 per share)	(61,237)			(61,237)
Other comprehensive loss	173,626				173,626
Settlement of convertible notes (in shares)		928				(503)
Settlement of convertible notes	4,832	$ 928	(48,375)			$ 52,279
Settlement of note hedges associated with convertible notes (in shares)						516
Settlement of note hedges associated with convertible notes and warrants	(7)		112,901			$ (112,908)
Shares issued under compensation plans (in shares)		129				(48)
Shares issued under compensation plans	23,182	$ 129	20,395			$ 2,658
Deferred compensation (in shares)						(2)
Deferred compensation	88					$ 88
Ending Balance (in shares) at Dec. 31, 2017		46,871				1,704
Ending Balance at Dec. 31, 2017	$ 2,430,531	$ 46,871	$ 591,721	$ 2,285,886	$ (265,091)	$ (228,856)	$ 0