Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands	Stock Issued to Directors [Member] Common Stock [Member]	Stock Issued to Directors [Member] Additional Paid-in Capital [Member]	Stock Issued to Directors [Member]	Stock Issued for 401(K) Match [Member] Common Stock [Member]	Stock Issued for 401(K) Match [Member] Additional Paid-in Capital [Member]	Stock Issued for 401(K) Match [Member]	Series B Preferred Stock [Member] 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, 2014							$ 39	$ 92,382	$ 1,486,750	$ (141,306)	$ (32,031)	$ (8,860)	$ 1,396,974
Net Income (Loss)										(86,968)			(86,968)
Stock issued to directors	$ 59	$ 547	$ 606					218	2,808				3,026
Series B Preferred Stock dividends declared										(552)			(552)
Stock issued for 401(k) match				$ 333	$ 3,114	$ 3,447		441	4,569				5,010
Restricted stock units granted									4,819				4,819
Restricted stock unit distributions								224	(224)			(934)	(934)
Common stock issued for purchase of another company								1,562	17,215				18,777
Common stock dividends declared										(3,739)			(3,739)
Repurchase of common shares												(940)	(940)
Other comprehensive loss											(600)		(600)
Balance at Dec. 31, 2015							39	95,219	1,519,598	(232,565)	(32,631)	(10,734)	1,338,926
Net Income (Loss)										69,547			69,547
Stock issued to directors	47	756	803					545	5,188			(1,270)	4,463
Series B Preferred Stock dividends declared										(552)			(552)
Stock issued for 401(k) match				282	3,236	3,518		457	7,230				7,687
Restricted stock units granted									5,128				5,128
Restricted stock unit distributions								348	(348)			(2,211)	(2,211)
Common stock issued for purchase of another company								2,213	48,998			(959)	50,252
Common stock dividends declared										(3,867)			(3,867)
Other comprehensive loss											(1,971)		(1,971)
Common stock issued for cash, net of offering costs								695	7,426				8,121
Balance at Dec. 31, 2016							39	99,806	1,597,212	(167,437)	(34,602)	(15,174)	1,479,844
Net Income (Loss)										(23,519)			(23,519)
Stock issued to directors	$ 47	$ 735	$ 782					133	4,107			(669)	3,571
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)
Other comprehensive loss											11,229		11,229
Common stock issued for cash, net of offering costs								457	9,154				9,611
Balance at Dec. 31, 2017							$ 39	$ 100,926	$ 1,619,816	$ (195,484)	$ (23,373)	$ (18,042)	$ 1,483,882