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, 2017	$ 39	$ 100,926	$ 1,619,816	$ (218,089)	$ (23,373)	$ (18,042)	$ 1,461,277
Net (loss) income				20,314			20,314
Restricted stock units granted			2,404				2,404
Common stock dividends declared ($0.0025 per common share)				(2,000)			(2,000)
Series B Preferred Stock dividends declared ($0.875 per share)				(276)			(276)
Common stock issued for 401(k) match		138	1,936				2,074
Common stock issued for employee incentive compensation		309	4,554			(1,225)	3,638
Other comprehensive income (loss)					(7,267)		(7,267)
Restricted stock unit distributions		270	(270)			(1,469)	(1,469)
Change in accounting for marketable equity securities				1,289	(1,289)
Balance at Jun. 30, 2018	39	101,643	1,628,440	(198,762)	(31,929)	(20,736)	1,478,695
Balance at Mar. 31, 2018	39	101,290	1,626,298	(209,696)	(26,767)	(19,267)	1,471,897
Net (loss) income				12,074			12,074
Restricted stock units granted			1,315				1,315
Common stock dividends declared ($0.0025 per common share)				(1,002)			(1,002)
Series B Preferred Stock dividends declared ($0.875 per share)				(138)			(138)
Common stock issued for 401(k) match		83	1,097				1,180
Other comprehensive income (loss)					(5,162)		(5,162)
Restricted stock unit distributions		270	(270)			(1,469)	(1,469)
Balance at Jun. 30, 2018	39	101,643	1,628,440	(198,762)	(31,929)	(20,736)	1,478,695
Balance at Dec. 31, 2018	39	121,956	1,880,481	(248,308)	(42,469)	(20,736)	1,690,963
Net (loss) income				(72,065)			(72,065)
Restricted stock units granted			3,097				3,097
Common stock dividends declared ($0.0025 per common share)				(2,430)			(2,430)
Series B Preferred Stock dividends declared ($0.875 per share)				(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			3,003				3,600
Common stock issued to directors		63	392				455
Other comprehensive income (loss)					7,799		7,799
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) income				(46,532)			(46,532)
Restricted stock units granted			1,518				1,518
Common stock dividends declared ($0.0025 per common share)				(1,221)			(1,221)
Series B Preferred Stock dividends declared ($0.875 per share)				(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
Common stock issued to directors		63	392				455
Other comprehensive income (loss)					3,540		3,540
Balance at Jun. 30, 2019	$ 39	$ 123,701	$ 1,895,617	$ (323,079)	$ (34,670)	$ (22,380)	$ 1,639,228