CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Common Stock	Retained Earnings Adoption of ASU 2017-08 Revision of Prior Period, Adjustment	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Treasury Stock	Total Stockholders' Equity Adoption of ASU 2017-08 Revision of Prior Period, Adjustment	Total Stockholders' Equity	Noncontrolling Interest	Adoption of ASU 2017-08 Revision of Prior Period, Adjustment	Total
Balance at Dec. 31, 2018	$ 112,383		$ 419,179	$ (6,191)	$ (3,756)		$ 521,615	$ 89		$ 521,704
Balance (in shares) at Dec. 31, 2018	25,128,773
Increase (Decrease) in Stockholders' Equity
Net income			64,849				64,849			64,849
Other comprehensive income, net of tax				19,658			19,658			19,658
Cash dividends declared			(21,965)				(21,965)			(21,965)
Cashless exercise of warrants	$ 0						0			0
Cashless exercise of warrants (in shares)	224,066
Treasury shares purchased under deferred directors' plan	$ 461				(461)		0			0
Treasury shares purchased under deferred directors' plan (in shares)	(10,356)
Treasury shares sold and distributed under deferred directors' plan	$ (118)				118		0			0
Treasury shares sold and distributed under deferred directors' plan (in shares)	5,699
Stock activity under equity compensation plans	$ (2,109)						(2,109)			(2,109)
Stock activity under equity compensation plans (in shares)	97,218
Stock based compensation expense	$ 3,626						3,626			3,626
Balance at Sep. 30, 2019	$ 114,243		460,736	13,467	(4,099)		584,347	89		584,436
Balance (in shares) at Sep. 30, 2019	25,445,400
Balance at Jun. 30, 2019	$ 112,689		446,969	9,500	(3,884)		565,274	89		565,363
Balance (in shares) at Jun. 30, 2019	25,442,300
Increase (Decrease) in Stockholders' Equity
Net income			21,454				21,454			21,454
Other comprehensive income, net of tax				3,967			3,967			3,967
Cash dividends declared			(7,687)				(7,687)			(7,687)
Treasury shares purchased under deferred directors' plan	$ 215			0	(215)		0			0
Treasury shares purchased under deferred directors' plan (in shares)	(4,700)
Stock activity under equity compensation plans	$ (20)						(20)			(20)
Stock activity under equity compensation plans (in shares)	7,800
Stock based compensation expense	$ 1,359						1,359			1,359
Balance at Sep. 30, 2019	$ 114,243		460,736	13,467	(4,099)		584,347	89		584,436
Balance (in shares) at Sep. 30, 2019	25,445,400
Increase (Decrease) in Stockholders' Equity
Cumulative period adjustment made to retained earnings		$ (1,327)				$ (1,327)			$ (1,327)
Cumulative period adjustment made to retained earnings										475,247
Balance at Dec. 31, 2019	$ 114,858		475,247	12,059	(4,153)		598,011	89		$ 598,100
Balance (in shares) at Dec. 31, 2019	25,444,275									25,444,275
Increase (Decrease) in Stockholders' Equity
Net income			59,745				59,745			$ 59,745
Other comprehensive income, net of tax				13,165			13,165			13,165
Cash dividends declared			(22,951)				(22,951)			(22,951)
Treasury shares purchased under share repurchase plan	$ 0				(10,012)		(10,012)			(10,012)
Treasury shares purchased under share repurchase plan (in shares)	(289,101)
Treasury shares purchased under deferred directors' plan	$ 480				(480)		0			0
Treasury shares purchased under deferred directors' plan (in shares)	(10,450)
Treasury shares sold and distributed under deferred directors' plan	$ (119)				119		0			0
Treasury shares sold and distributed under deferred directors' plan (in shares)	5,748
Stock activity under equity compensation plans	$ (2,030)						(2,030)			(2,030)
Stock activity under equity compensation plans (in shares)	85,899
Stock based compensation expense	$ 822						822			822
Balance at Sep. 30, 2020	$ 114,011		512,041	25,224	(14,526)		636,750	89		$ 636,839
Balance (in shares) at Sep. 30, 2020	25,236,371									25,236,371
Balance at Jun. 30, 2020	$ 113,424		496,891	24,802	(14,314)		620,803	89		$ 620,892
Balance (in shares) at Jun. 30, 2020	25,233,280
Increase (Decrease) in Stockholders' Equity
Net income			22,776				22,776			22,776
Other comprehensive income, net of tax				422			422			422
Cash dividends declared			(7,626)				(7,626)			(7,626)
Treasury shares purchased under deferred directors' plan	$ 212				(212)		0			0
Treasury shares purchased under deferred directors' plan (in shares)	(4,709)
Stock activity under equity compensation plans	$ 0						0			0
Stock activity under equity compensation plans (in shares)	7,800
Stock based compensation expense	$ 375						375			375
Balance at Sep. 30, 2020	$ 114,011		$ 512,041	$ 25,224	$ (14,526)		$ 636,750	$ 89		$ 636,839
Balance (in shares) at Sep. 30, 2020	25,236,371									25,236,371
Increase (Decrease) in Stockholders' Equity
Cumulative period adjustment made to retained earnings										$ 512,041