CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY (Unaudited) - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid In Capital	Retained Earnings	Accumulated Other Comprehensive Loss	Treasury Stock
Beginning Balance (in shares) at Dec. 31, 2017		46,871				1,704
Beginning Balance at Dec. 31, 2017	$ 2,430,531	$ 46,871	$ 591,721	$ 2,285,886	$ (265,091)	$ (228,856)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	56,184			56,184
Cash dividends	(15,447)			(15,447)
Other comprehensive (loss) income	82,690				82,690
Shares issued under compensation plans (in shares)		(97)				(43)
Shares issued under compensation plans	4,122	$ 97	992			$ 3,033
Deferred compensation (in shares)						(8)
Deferred compensation	322					$ 322
Settlements of warrants (in shares)						(132)
Settlements of warrants	(12)		(17,884)			$ 17,872
Ending Balance (in shares) at Apr. 01, 2018		46,968				1,521
Ending Balance at Apr. 01, 2018	2,561,466	$ 46,968	574,829	2,329,699	(182,401)	$ (207,629)
Beginning Balance (in shares) at Dec. 31, 2017		46,871				1,704
Beginning Balance at Dec. 31, 2017	2,430,531	$ 46,871	591,721	2,285,886	(265,091)	$ (228,856)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	53,688
Other comprehensive (loss) income	(41,329)
Ending Balance (in shares) at Jul. 01, 2018		47,082				1,379
Ending Balance at Jul. 01, 2018	2,433,981	$ 47,082	570,037	2,311,712	(306,420)	$ (188,430)
Beginning Balance (in shares) at Apr. 01, 2018		46,968				1,521
Beginning Balance at Apr. 01, 2018	2,561,466	$ 46,968	574,829	2,329,699	(182,401)	$ (207,629)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(2,496)			(2,496)
Cash dividends	(15,491)			(15,491)
Other comprehensive (loss) income	(124,019)				(124,019)
Shares issued under compensation plans (in shares)		(114)				(2)
Shares issued under compensation plans	14,300	$ 114	13,992			$ 194
Deferred compensation	235		235
Settlements of warrants (in shares)						(140)
Settlements of warrants	(14)		(19,019)			$ 19,005
Ending Balance (in shares) at Jul. 01, 2018		47,082				1,379
Ending Balance at Jul. 01, 2018	2,433,981	$ 47,082	570,037	2,311,712	(306,420)	$ (188,430)
Beginning Balance (in shares) at Dec. 31, 2018		47,248				1,232
Beginning Balance at Dec. 31, 2018	2,539,978	$ 47,248	574,761	2,427,599	(341,085)	$ (168,545)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	40,897			40,897
Cash dividends	(15,650)			(15,650)
Other comprehensive (loss) income	396				396
Shares issued under compensation plans (in shares)		(75)				(40)
Shares issued under compensation plans	5,198	$ 75	3,094			$ 2,029
Deferred compensation (in shares)						(4)
Deferred compensation	380		127			$ 253
Ending Balance (in shares) at Mar. 31, 2019		47,323				1,188
Ending Balance at Mar. 31, 2019	2,569,878	$ 47,323	577,982	2,451,525	(340,689)	$ (166,263)
Beginning Balance (in shares) at Dec. 31, 2018		47,248				1,232
Beginning Balance at Dec. 31, 2018	2,539,978	$ 47,248	574,761	2,427,599	(341,085)	$ (168,545)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	124,272
Other comprehensive (loss) income	15,178
Ending Balance (in shares) at Jun. 30, 2019		47,400				1,186
Ending Balance at Jun. 30, 2019	2,664,844	$ 47,400	590,234	2,519,203	(325,907)	$ (166,086)
Beginning Balance (in shares) at Mar. 31, 2019		47,323				1,188
Beginning Balance at Mar. 31, 2019	2,569,878	$ 47,323	577,982	2,451,525	(340,689)	$ (166,263)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	83,375			83,375
Cash dividends	(15,697)			(15,697)
Other comprehensive (loss) income	14,782				14,782
Shares issued under compensation plans (in shares)		(77)				(2)
Shares issued under compensation plans	12,506	$ 77	12,252			$ 177
Ending Balance (in shares) at Jun. 30, 2019		47,400				1,186
Ending Balance at Jun. 30, 2019	$ 2,664,844	$ 47,400	$ 590,234	$ 2,519,203	$ (325,907)	$ (166,086)