CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY (Unaudited) - USD ($) $ in Thousands	Total	Series D Preferred Stock	Preferred Stock	Preferred Stock Series D Preferred Stock	Common Stock	Capital Surplus	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Treasury Stock
Balance at beginning of period at Dec. 31, 2016	$ 740,916		$ 1,357		$ 26,120	$ 328,376	$ 416,109	$ (31,046)	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income	46,617						39,968	6,649
Cash dividends declared:
Preferred	(32)						(32)
Common	(5,817)						(5,817)
Conversion of Series D preferred stock		$ (419)		$ (419)
Purchase of shares of common stock	(217)								(217)
Issuance of shares of common stock	22,159				581	21,361			217
Stock based compensation	2,763					2,763
Balance at end of period at Jun. 30, 2017	805,970		938		26,701	352,500	450,228	(24,397)	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Reclassification of unrealized net gain on equity securities	0						280	(280)
Balance at beginning of period at Dec. 31, 2017	991,457		938		29,953	503,709	481,331	(24,474)	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income	31,358						51,147	(19,789)
Cash dividends declared:
Preferred	(26)						(26)
Common	(7,946)						(7,946)
Purchase of shares of common stock	(97)								(97)
Issuance of shares of common stock	238,231				4,485	233,649			97
Stock based compensation	2,770					2,770
Balance at end of period at Jun. 30, 2018	$ 1,255,747		$ 938		$ 34,438	$ 740,128	$ 524,786	$ (44,543)	$ 0