Consolidated Statements of Changes in Stockholders' Equity - 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, 2016	$ 39	$ 99,806	$ 1,597,212	$ (185,041)	$ (34,602)	$ (15,174)	$ 1,462,240
Net income (loss)				(28,520)			(28,520)
Stock issued to directors		47	735				782
Common stock issued for cash, net of offering costs		457	9,154				9,611
Series B Preferred Stock dividends declared				(552)			(552)
Stock issued for 401(k) match		170	3,379				3,549
Restricted stock units granted			5,550				5,550
Restricted stock unit distributions		313	(321)			(2,199)	(2,207)
Common stock dividends declared				(3,976)			(3,976)
Common stock issued for employee incentive compensation		133	4,107			(669)	3,571
Other comprehensive income (loss)					11,229		11,229
Balance at Dec. 31, 2017	39	100,926	1,619,816	(218,089)	(23,373)	(18,042)	1,461,277
Net income (loss)				(26,563)			(26,563)
Stock issued to directors		40	553				593
Common stock issued for cash, net of offering costs		641	6,105				6,746
Series B Preferred Stock dividends declared				(552)			(552)
Stock issued for 401(k) match		267	3,438				3,705
Restricted stock units granted			5,649				5,649
Restricted stock unit distributions		270	(270)			(1,386)	(1,386)
Common stock dividends declared				(4,393)			(4,393)
Common stock issued for employee incentive compensation		309	4,554			(1,308)	3,555
Other comprehensive income (loss)					(17,807)		(17,807)
Change in accounting for marketable equity securities				1,289	(1,289)
Common stock issued to pension plans		684	6,911				7,595
Common stock issued for purchase of another company		18,819	233,725				252,544
Balance at Dec. 31, 2018	39	121,956	1,880,481	(248,308)	(42,469)	(20,736)	1,690,963
Net income (loss)				(99,557)			(99,557)
Stock issued to directors		63	392				455
Common stock issued for cash, net of offering costs		5,353	43,666				49,019
Series B Preferred Stock dividends declared				(552)			(552)
Stock issued for 401(k) match		470	3,392				3,862
Restricted stock units granted			5,213				5,213
Restricted stock unit distributions		291	(291)			(636)	(636)
Common stock dividends declared				(4,914)			(4,914)
Common stock issued for employee incentive compensation		899	7,375			(1,595)	6,679
Other comprehensive income (loss)					5,159		5,159
Common stock issued to pension plans		596	3,004				3,600
Common stock issued for prepayment of debt (10,655,000 shares)		2,664	30,793				33,457
Adjustment to fair value of warrants issued for purchase of another company			(325)				(325)
Balance at Dec. 31, 2019	$ 39	$ 132,292	$ 1,973,700	$ (353,331)	$ (37,310)	$ (22,967)	$ 1,692,423