Consolidated Statement of Changes in Stockholders' Equity - USD ($) $ in Thousands		Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Accumulated Other Comprehensive Income (Loss) [Member] Revision of Prior Period, Change in Accounting Principle, Adjustment [Member]	Retained Earnings [Member]	Retained Earnings [Member] Revision of Prior Period, Change in Accounting Principle, Adjustment [Member]	Treasury Stock [Member]
Balance at Dec. 31, 2017		$ 373,286	$ 127	$ 160,940	$ 217	$ 47	$ 262,900	$ (47)	$ (50,898)
Balance (In shares) at Dec. 31, 2017	[1]		20,312,082
Net income		46,249					46,249
Other comprehensive income (loss)		(2,412)			(2,412)
Deferred compensation plan		636							636
Stock based compensation expense		420		420
Shares issued under stock option plan, net		111		(93)			(270)		474
Shares issued under stock option plan, net (In shares)	[1]		38,628
Restricted share issuance/ Restricted share activity under stock incentive plans		568		258			(201)		511
Restricted share issuance/Restricted share activity under stock incentive plan (In shares)	[1]		48,300
Shares issued from direct stock sales		104		68					36
Shares issued from direct stock sales (In shares)	[1]		3,542
Shares repurchased		(6,330)							(6,330)
Shares repurchased (In Shares)	[1]		(231,160)
Common stock dividends paid		(13,043)					(13,043)
Balance at Dec. 31, 2018		399,589	$ 127	161,593	(2,148)		295,588		(55,571)
Balance (In shares) at Dec. 31, 2018	[1]		20,171,392
Net income		49,370					49,370
Other comprehensive income (loss)		6,743			6,743
Deferred compensation plan		78		(80)					158
Stock based compensation expense		286		286
Shares issued under stock option plan, net		189		(32)			(5)		226
Shares issued under stock option plan, net (In shares)	[1]		19,022
Restricted share issuance/ Restricted share activity under stock incentive plans		560		117			(154)		597
Restricted share issuance/Restricted share activity under stock incentive plan (In shares)	[1]		51,194
Shares issued from direct stock sales		123		71					52
Shares issued from direct stock sales (In shares)	[1]		4,255
Shares repurchased		(15,147)							(15,147)
Shares repurchased (In Shares)	[1]		(515,977)
Common stock dividends paid		(15,624)					(15,624)
Balance at Dec. 31, 2019		426,167	$ 127	161,955	4,595		329,175		(69,685)
Balance (In shares) at Dec. 31, 2019	[1]		19,729,886
Net income		63,077					63,077
Other comprehensive income (loss)		10,409			10,409
Adoption of ASC 326		(2,566)					(2,566)
Deferred compensation plan				24					(24)
Deferred compensation plan (In shares)	[1]		7,524
Stock based compensation expense		2,312		2,312
Capital stock issuance related to acquisition		527,311	$ 179	527,132
Capital stock issuance (In shares)	[1]		17,926,174
Vesting of incentive plans		(1,371)		(1,864)					493
Vesting of incentive plans (In shares)	[1]		39,548
Shares issued under stock option plan, net				(122)					122
Shares issued under stock option plan, net (In shares)	[1]		11,408
Restricted share issuance/ Restricted share activity under stock incentive plans				198			(374)		176
Restricted share issuance/Restricted share activity under stock incentive plan (In shares)	[1]		13,349
Restricted share forfeitures				13					(13)
Restricted share forfeitures (In shares)	[1]		(2,265)
Shares issued from direct stock sales		18							18
Shares issued from direct stock sales (In shares)	[1]		1,148
Shares repurchased		(10,183)							(10,183)
Shares repurchased (In Shares)	[1]		(435,292)
Common stock dividends paid		(32,898)					(32,898)
Other, net				(258)					258
Balance at Dec. 31, 2020		$ 982,276	$ 306	$ 689,390	$ 15,004		$ 356,414		$ (78,838)
Balance (In shares) at Dec. 31, 2020	[1]		37,291,480

[1] Share data has been adjusted to reflect a 2-for-1 stock split on July 12, 2018.