Consolidated Statements of Changes in Equity - USD ($) $ in Thousands	Total	Series C Preferred Stock	Series D Preferred Stock	Preferred Stock	Preferred Stock Series C Preferred Stock	Preferred Stock Series D Preferred Stock	Common Stock	Capital Surplus	Retained Earnings	Retained Earnings Series C Preferred Stock	Retained Earnings Series D Preferred Stock	Accumulated Other Comprehensive Income (Loss)	Treasury Stock
Balance at beginning of period at Dec. 31, 2015	$ 663,173			$ 81,698			$ 22,436	$ 216,436	$ 348,630			$ (6,027)	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income (loss)	55,330								80,349			(25,019)
Cash dividends declared:
Preferred		$ (168)	$ (124)							$ (168)	$ (124)
Common	(12,578)								(12,578)
Redemption of preferred stock		$ (81,698)	(2,420)		$ (81,698)	$ (2,420)
Issuance of preferred stock			3,777			3,777
Purchase of shares of treasury stock	(3,719)												(3,719)
Issuance of shares of common stock	115,865						3,684	108,462					3,719
Stock based compensation	3,478							3,478
Balance at end 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 (loss)	86,351								75,272			11,079
Reclassification of certain income tax effects from accumulated other comprehensive income (loss)									4,507			(4,507)
Cash dividends declared:
Preferred			(58)								(58)
Common	(14,499)								(14,499)
Redemption of preferred stock			(419)			(419)
Purchase of shares of treasury stock	(625)												(625)
Issuance of shares of common stock	175,723						3,833	171,265					625
Stock based compensation	4,068							4,068
Balance at end 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]
Reclassification of unrealized net gain on equity securities	0								280			(280)
Comprehensive income (loss)	110,103								116,998			(6,895)
Cash dividends declared:
Preferred			(39)								$ (39)
Common	(19,318)								(19,318)
Purchase of shares of treasury stock	(97)												(97)
Issuance of shares of common stock	239,502						4,524	234,881					97
Stock based compensation	4,505							4,505
Conversion of Series D preferred stock			$ (938)			$ (938)
Balance at end of period at Dec. 31, 2018	$ 1,325,175			$ 0			$ 34,477	$ 743,095	$ 579,252			$ (31,649)	$ 0