Condensed Consolidated Statements of Changes in Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Preferred Stock [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	AOCI Attributable to Parent [Member]	Treasury Stock [Member]	Total
Balance at Dec. 31, 2018	$ 39	$ 121,956	$ 1,880,481	$ (248,308)	$ (42,469)	$ (20,736)	$ 1,690,963
Net loss				(72,065)			(72,065)
Restricted stock units granted			3,097				3,097
Common stock dividends declared				(2,430)			(2,430)
Series B Preferred Stock dividends declared				(276)			(276)
Common stock issued for 401(k) match		186	1,594				1,780
Common stock issued for employee incentive compensation		899	7,375			(1,644)	6,630
Common stock issued to pension plans		597	3,003				3,600
Other comprehensive income (loss)					7,799		7,799
Common stock issued to directors		63	392				455
Adjustment to fair value of warrants issued for purchase of another company			(325)				(325)
Balance at Jun. 30, 2019	39	123,701	1,895,617	(323,079)	(34,670)	(22,380)	1,639,228
Balance at Mar. 31, 2019	39	122,052	1,882,613	(275,188)	(38,210)	(20,736)	1,670,570
Net loss				(46,532)			(46,532)
Restricted stock units granted			1,518				1,518
Common stock dividends declared				(1,221)			(1,221)
Series B Preferred Stock dividends declared				(138)			(138)
Common stock issued for 401(k) match		90	716				806
Common stock issued for employee incentive compensation		899	7,375			(1,644)	6,630
Common stock issued to pension plans		597	3,003				3,600
Other comprehensive income (loss)					3,540		3,540
Common stock issued to directors		63	392				455
Balance at Jun. 30, 2019	39	123,701	1,895,617	(323,079)	(34,670)	(22,380)	1,639,228
Balance at Dec. 31, 2019	39	132,292	1,973,700	(353,331)	(37,310)	(22,967)	1,692,423
Net loss				(31,213)			(31,213)
Restricted stock units granted			2,430				2,430
Restricted stock units distributed		426	(426)			(1,479)	(1,479)
Common stock dividends declared				(2,622)			(2,622)
Series B Preferred Stock dividends declared				(276)			(276)
Common stock issued for 401(k) match		240	1,992				2,232
Common stock issued for employee incentive compensation		699	4,396			(1,266)	3,829
Common stock issued to pension plans		42	308				350
Treasury shares issued to charitable foundation (650,000 shares)				(246)		2,216	1,970
Treasury shares issued to charitable foundation (650,000 shares)				(246)		2,216	1,970
Other comprehensive income (loss)	0	0	0	0	(8,951)	0	(8,951)
Balance at Jun. 30, 2020	39	133,699	1,982,400	(387,688)	(46,261)	(23,496)	1,658,693
Balance at Mar. 31, 2020	39	132,381	1,976,033	(371,958)	(56,645)	(22,967)	1,656,883
Net loss				(14,028)			(14,028)
Restricted stock units granted			1,211				1,211
Restricted stock units distributed		426	(426)			(1,479)	(1,479)
Common stock dividends declared				(1,318)			(1,318)
Series B Preferred Stock dividends declared				(138)			(138)
Common stock issued for 401(k) match		151	878				1,029
Common stock issued for employee incentive compensation		699	4,396			(1,266)	3,829
Common stock issued to pension plans		42	308				350
Treasury shares issued to charitable foundation (650,000 shares)				(246)		2,216	1,970
Treasury shares issued to charitable foundation (650,000 shares)				(246)		2,216	1,970
Other comprehensive income (loss)					10,384		10,384
Balance at Jun. 30, 2020	$ 39	$ 133,699	$ 1,982,400	$ (387,688)	$ (46,261)	$ (23,496)	$ 1,658,693