Consolidated Statements of Changes in Equity (Unaudited) - USD ($) $ in Thousands	Total	Preferred Stock [Member]	Common Stock [Member]	Capital Surplus [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Treasury Stock [Member]
Balance at beginning of period at Dec. 31, 2013	$ 439,460	$ 81,698	$ 18,399	$ 91,632	$ 265,067	$ (17,336)	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income	35,289				17,664	17,625
Cash dividends declared:
Preferred	(408)				(408)
Common	(3,691)				(3,691)
Purchase of shares of common stock	(608)						(608)
Issuance of shares of common stock	548		69	(129)			608
Commitments to issue common stock	1,831			1,831
Balance at end of period at Jun. 30, 2014	472,421	81,698	18,468	93,334	278,632	289	0
Balance at beginning of period at Dec. 31, 2014	496,317	81,698	18,511	95,816	298,764	1,528	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income	32,400				30,869	1,531
Cash dividends declared:
Preferred	(408)				(408)
Common	(4,119)				(4,119)
Purchase of shares of common stock	(2,173)						(2,173)
Issuance of shares of common stock	55,281		2,105	51,065			2,111
Commitments to issue common stock	1,908			1,908
Balance at end of period at Jun. 30, 2015	$ 579,206	$ 81,698	$ 20,616	$ 148,789	$ 325,106	$ 3,059	$ (62)