Consolidated Statements of Changes in Equity (Unaudited) - 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	64,135								61,187			2,948
Cash dividends declared:
Preferred		$ (168)	$ (105)							$ (168)	$ (105)
Common	(7,365)								(7,365)
Redemption of Preferred Stock					$ (81,698)	$ (2,420)
Issuance of Series D Preferred Stock						3,777
Purchase of shares of common stock	(2,293)												(2,293)
Issuance of shares of common stock	64,279						2,247	59,807					2,225
Stock based compensation	3,073							3,073
Balance at end of period at Sep. 30, 2016	704,388			1,357			24,683	279,316	402,179			(3,079)	(68)
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	71,628								61,600			10,028
Cash dividends declared:
Preferred			$ (45)								$ (45)
Common	(9,108)								(9,108)
Conversion of Series D preferred stock						$ (419)
Purchase of shares of common stock	(440)												(440)
Issuance of shares of common stock	175,564						3,826	171,298					440
Stock based compensation	3,588							3,588
Balance at end of period at Sep. 30, 2017	$ 981,684			$ 938			$ 29,946	$ 503,262	$ 468,556			$ (21,018)	$ 0