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, 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 ($0.30 per share)				(9,204)			(9,204)
Redemption of preferred stock	(11,250)						(11,250)
Exercise of stock options (136,429, 66,389 and 189,992) shares)			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 (70,019, 57,164 and 24,018 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 ($0.30 per share)				(9,657)			(9,657)
Issuance costs of common stock		(180)					(180)
Exercise of stock options (136,429, 66,389 and 189,992) shares)			417				417
Restricted stock, net of forfeitures (70,019, 57,164 and 24,018 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
Reclassification of stranded tax effects (ASU 2018-02) (see Note 17)				709		709
Cumulative effect of adopting ASU 2016-01 (see Note 17)				(55)		55
Net income				60,352			60,352
Other comprehensive loss, net of taxes						(4,116)	(4,116)
Cash dividends declared on common stock ($0.30 per share)				(9,686)			(9,686)
Exercise of stock options (136,429, 66,389 and 189,992) shares)			875				875
Restricted stock, net of forfeitures (70,019, 57,164 and 24,018 shares)
Net shares issued in satisfaction of performance units earned, (42,672 shares)			(819)				(819)
Stock-based compensation expense			$ 1,884				$ 1,884
Balance at Dec. 31, 2018		$ 412,546	$ 15,542	$ 211,345	$ (16,717)	$ (8,789)	$ 613,927