CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Common Stock [Member]	Additional Paid-In Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Total
Balance at Dec. 31, 2017	$ 239	$ 304,932	$ 18,753	$ (1,152)	$ 322,772
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income			25,987		25,987
Changes in other comprehensive income (loss) on investment securities, net of tax and accreation				(2,803)	(2,803)
Dividends on common stock			(5,764)		(5,764)
Issuance of common stock under Stock Incentive Plan	1	324			325
Stock-based compensation expense		327			327
Reclassification from accumulated other comprehensive loss to retained earnings due to adoption of ASU 2018-02			229	(229)
Balance at Sep. 30, 2018	240	305,583	39,205	(4,184)	340,844
Balance at Jun. 30, 2018	240	305,460	32,269	(3,519)	334,450
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income			8,861		8,861
Changes in other comprehensive income (loss) on investment securities, net of tax and accreation				(665)	(665)
Dividends on common stock			(1,925)		(1,925)
Issuance of common stock under Stock Incentive Plan		(35)			(35)
Stock-based compensation expense		158			158
Balance at Sep. 30, 2018	240	305,583	39,205	(4,184)	340,844
Balance at Dec. 31, 2018	240	305,654	44,985	(2,589)	348,290
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income			24,203		24,203
Changes in other comprehensive income (loss) on investment securities, net of tax and accreation				3,695	3,695
Dividends on common stock			(6,514)		(6,514)
Issuance of common stock under Stock Incentive Plan	1	603			604
Stock-based compensation expense		352			352
Balance at Sep. 30, 2019	241	306,609	62,674	1,106	370,630
Balance at Jun. 30, 2019	241	306,049	55,983	519	362,792
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income			8,864		8,864
Changes in other comprehensive income (loss) on investment securities, net of tax and accreation				587	587
Dividends on common stock			(2,173)		(2,173)
Issuance of common stock under Stock Incentive Plan		475			475
Stock-based compensation expense		85			85
Balance at Sep. 30, 2019	$ 241	$ 306,609	$ 62,674	$ 1,106	$ 370,630