CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY (UNAUDITED) - USD ($) $ in Thousands	Total	Common Stock	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Cumulative Effect, Period of Adoption, Adjustment	Cumulative Effect, Period of Adoption, Adjustment Retained Earnings
Beginning Balance (in shares) at Dec. 31, 2018		15,591,914
Beginning Balance at Dec. 31, 2018	$ 435,825	$ 158,215	$ 302,030	$ (24,420)	$ 254	$ 254
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	27,477		27,477
Other comprehensive income, net of tax	19,957			19,957
Stock-based compensation expense	935	$ 935
Exercise of stock options and issuance of vested share awards, net of repurchase for tax withholdings and tax benefit (shares)		32,344
Exercise of stock options and issuance of vested share awards, net of repurchase for tax withholdings	(241)	$ (241)
Cash dividends declared	(9,340)		(9,340)
Common stock repurchased	(7,108)	$ (7,108)
Common stock repurchased (in shares)		(166,778)
Ending Balance (in shares) at Jun. 30, 2019		15,457,480
Ending Balance at Jun. 30, 2019	467,759	$ 151,801	320,421	(4,463)
Beginning Balance (in shares) at Mar. 31, 2019		15,560,565
Beginning Balance at Mar. 31, 2019	453,718	$ 156,152	311,870	(14,304)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	13,204		13,204
Other comprehensive income, net of tax	9,841			9,841
Stock-based compensation expense	477	$ 477
Exercise of stock options and issuance of vested share awards, net of repurchase for tax withholdings and tax benefit (shares)		8,136
Exercise of stock options and issuance of vested share awards, net of repurchase for tax withholdings	(26)	$ (26)
Cash dividends declared	(4,653)		(4,653)
Common stock repurchased	(4,802)	$ (4,802)
Common stock repurchased (in shares)		(111,221)
Ending Balance (in shares) at Jun. 30, 2019		15,457,480
Ending Balance at Jun. 30, 2019	467,759	$ 151,801	320,421	(4,463)
Beginning Balance (in shares) at Dec. 31, 2019		15,144,719
Beginning Balance at Dec. 31, 2019	473,415	$ 139,103	340,580	(6,268)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	24,433		24,433
Other comprehensive income, net of tax	25,624			25,624
Stock-based compensation expense	951	$ 951
Exercise of stock options and issuance of vested share awards, net of repurchase for tax withholdings and tax benefit (shares)		35,353
Exercise of stock options and issuance of vested share awards, net of repurchase for tax withholdings	(100)	$ (100)
Cash dividends declared	(9,883)		(9,883)
Common stock repurchased	(7,973)	$ (7,973)
Common stock repurchased (in shares)		(217,031)
Ending Balance (in shares) at Jun. 30, 2020		14,963,041
Ending Balance at Jun. 30, 2020	506,467	$ 131,981	355,130	19,356
Beginning Balance (in shares) at Mar. 31, 2020		14,951,597
Beginning Balance at Mar. 31, 2020	492,680	$ 131,498	349,141	12,041
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	10,940		10,940
Other comprehensive income, net of tax	7,315			7,315
Stock-based compensation expense	530	$ 530
Exercise of stock options and issuance of vested share awards, net of repurchase for tax withholdings and tax benefit (shares)		11,444
Exercise of stock options and issuance of vested share awards, net of repurchase for tax withholdings	(47)	$ (47)
Cash dividends declared	(4,951)		(4,951)
Ending Balance (in shares) at Jun. 30, 2020		14,963,041
Ending Balance at Jun. 30, 2020	$ 506,467	$ 131,981	$ 355,130	$ 19,356