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, 2015	$ 39	$ 95,219	$ 1,519,598	$ (242,191)	$ (32,631)	$ (10,734)	$ 1,329,300
Net income (loss)				61,569			61,569
Stock issued to directors		47	756				803
Common stock issued for cash, net of offering costs		695	7,426				8,121
Series B Preferred Stock dividends declared				(552)			(552)
Stock issued for 401(k) match		282	3,236				3,518
Restricted stock units granted			5,128				5,128
Restricted stock unit distributions		348	(348)			(2,211)	(2,211)
Common stock issued to pension plans		457	7,230				7,687
Common stock issued for purchase of another company		2,213	48,998			959	50,252
Common stock issued for purchase of another company		(2,213)	(48,998)			(959)	(50,252)
Common stock dividends declared				(3,867)			(3,867)
Common stock issued for employee incentive compensation		545	5,188			(1,270)	4,463
Change, net of tax					(1,971)		(1,971)
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
Change, net of tax					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 issued to pension plans		684	6,911				7,595
Common stock issued for purchase of another company		18,819	233,725				252,544
Common stock issued for purchase of another company		(18,819)	(233,725)				(252,544)
Common stock dividends declared				(4,393)			(4,393)
Common stock issued for employee incentive compensation		309	4,554			(1,308)	3,555
Change, net of tax					(17,807)		(17,807)
Change in accounting for marketable equity securities				1,289	(1,289)
Balance at Dec. 31, 2018	$ 39	$ 121,956	$ 1,880,481	$ (248,308)	$ (42,469)	$ (20,736)	$ 1,690,963