CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Preferred Stock [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Treasury Stock [Member]	Accumulated Other Comprehensive Income (Loss)	Total
Balance at Dec. 31, 2014	$ 11,250	$ 374,287	$ 6,015	$ 72,398	$ (16,717)	$ (1,014)	$ 446,219
Net income				41,311			41,311
Other comprehensive loss, net of taxes						(3,595)	(3,595)
Dividends on series B preferred stock				(112)			(112)
Cash dividends declared on common stock ($0.300 per share)				(8,991)			(8,991)
Exercise of stock options			1,765				1,765
Restricted stock net of forfeitures (69,258 and 70,019 shares)
Stock-based compensation expense			747				747
Balance at Dec. 31, 2015	11,250	374,287	8,527	104,606	(16,717)	(4,609)	477,344
Net income				31,082			31,082
Other comprehensive loss, net of taxes						1,763	1,763
Dividends on series B preferred stock				(22)			(22)
Cash dividends declared on common stock ($0.300 per share)				(9,204)			(9,204)
Redemption of preferred stock	(11,250)						(11,250)
Exercise of stock options			767				767
Secondary offering of common stock, net of costs of $1,811 (1,659,794 shares)		38,439					(38,439)
Restricted stock net of forfeitures (69,258 and 70,019 shares)
Stock-based compensation expense			2,113				2,113
Balance at Dec. 31, 2016		412,726	11,407	126,462	(16,717)	(2,846)	531,032
Net income				43,220			43,220
Other comprehensive loss, net of taxes						(1,173)	(1,173)
Cash dividends declared on common stock ($0.300 per share)				(9,657)			(9,657)
Issuance costs of common stock		(180)					(180)
Exercise of stock options			417				417
Restricted stock net of forfeitures (69,258 and 70,019 shares)
Stock-based compensation expense			1,778				1,778
Balance at Dec. 31, 2017		$ 412,546	$ 13,602	$ 160,025	$ (16,717)	$ (4,019)	$ 565,437