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	41,965		41,965
Other comprehensive income, net of tax	23,537			23,537
Stock-based compensation expense	1,364	$ 1,364
Exercise of stock options and issuance of vested share awards, net of repurchase for tax withholdings and tax benefit (shares)		37,202
Exercise of stock options and issuance of vested share awards, net of repurchase for tax withholdings	(190)	$ (190)
Common stock repurchased (in shares)		(404,213)
Common stock repurchased	(17,174)	$ (17,174)
Cash dividends declared	(13,909)		(13,909)
Ending Balance (in shares) at Sep. 30, 2019		15,224,903
Ending Balance at Sep. 30, 2019	471,672	$ 142,215	330,340	(883)
Beginning Balance (in shares) at Jun. 30, 2019		15,457,480
Beginning Balance at Jun. 30, 2019	467,759	$ 151,801	320,421	(4,463)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	14,488		14,488
Other comprehensive income, net of tax	3,580			3,580
Stock-based compensation expense	429	$ 429
Exercise of stock options and issuance of vested share awards, net of repurchase for tax withholdings and tax benefit (shares)		4,858
Exercise of stock options and issuance of vested share awards, net of repurchase for tax withholdings	51	$ 51
Common stock repurchased (in shares)		(237,435)
Common stock repurchased	(10,066)	$ (10,066)
Cash dividends declared	(4,569)		(4,569)
Ending Balance (in shares) at Sep. 30, 2019		15,224,903
Ending Balance at Sep. 30, 2019	471,672	$ 142,215	330,340	(883)
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	41,208		41,208
Other comprehensive income, net of tax	25,843			25,843
Stock-based compensation expense	1,373	$ 1,373
Exercise of stock options and issuance of vested share awards, net of repurchase for tax withholdings and tax benefit (shares)		37,571
Exercise of stock options and issuance of vested share awards, net of repurchase for tax withholdings	(113)	$ (113)
Common stock repurchased (in shares)		(264,946)
Common stock repurchased	(9,375)	$ (9,375)
Cash dividends declared	(14,829)		(14,829)
Ending Balance (in shares) at Sep. 30, 2020		14,917,344
Ending Balance at Sep. 30, 2020	517,522	$ 130,988	366,959	19,575
Beginning Balance (in shares) at Jun. 30, 2020		14,963,041
Beginning Balance at Jun. 30, 2020	506,467	$ 131,981	355,130	19,356
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	16,775		16,775
Other comprehensive income, net of tax	219			219
Stock-based compensation expense	422	$ 422
Exercise of stock options and issuance of vested share awards, net of repurchase for tax withholdings and tax benefit (shares)		2,218
Exercise of stock options and issuance of vested share awards, net of repurchase for tax withholdings	(13)	$ (13)
Common stock repurchased (in shares)		(47,915)
Common stock repurchased	(1,402)	$ (1,402)
Cash dividends declared	(4,946)		(4,946)
Ending Balance (in shares) at Sep. 30, 2020		14,917,344
Ending Balance at Sep. 30, 2020	$ 517,522	$ 130,988	$ 366,959	$ 19,575