Condensed Consolidated Statements of Stockholders' Equity (Unaudited) - USD ($) $ in Thousands		Total		Common Stock [Member]		Additional Paid-In Capital [Member]		Retained Earnings [Member]	Accumulated Other Comprehensive Loss [Member]	Deferred Compensation [Member]	Treasury Stock [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares Held In Trust For Deferred Compensation Plan		95,329
Common Stock, Dividends, Per Share, Declared		$ 1.285
Beginning Balances (shares) at Dec. 31, 2019	[1],[2]			16,403,776
Beginning Balances at Dec. 31, 2019		$ 561,577	[1],[2]	$ 7,984	[1],[2]	$ 259,253		$ 300,607	$ (6,267)	$ 4,543	$ (4,543)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income		49,146						49,146
Other comprehensive income (loss)		2,638							2,638
Other Comprehensive Income (Loss), Net of Tax		2,638
Dividend declared		(21,366)						(21,366)
Retirement savings plan and dividend reinvestment plan (shares)				258,260
Dividend reinvestment plan		21,819		$ 126		21,693
Share-based compensation (shares)	[3],[4]			34,456
Share-based compensation and tax benefit		2,906		$ 16	[3],[4]	2,890	[3],[4]
Treasury stock activities		0								1,091	(1,091)
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, QuantificationPrincipleEffectOfAdoptionQuantification		(30)						(30)
Ending Balances (shares) at Sep. 30, 2020	[1],[2]			16,696,492
Ending Balances at Sep. 30, 2020		$ 616,690	[1]	$ 8,126	[1]	283,836		328,357	(3,629)	5,634	(5,634)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based Payment Arrangement, Shares Withheld for Tax Withholding Obligation		10,319
Common Stock, Dividends, Per Share, Declared		$ 0.4400
Beginning Balances (shares) at Jun. 30, 2020	[1],[2]			16,463,808
Beginning Balances at Jun. 30, 2020		$ 593,277	[1]	$ 8,013	[1]	263,272		326,454	(4,462)	5,659	(5,659)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income		9,261						9,261
Other comprehensive income (loss)		833							833
Other Comprehensive Income (Loss), Net of Tax		833
Dividend declared		(7,358)						(7,358)
Retirement savings plan and dividend reinvestment plan (shares)				232,684
Dividend reinvestment plan		19,533		$ 113		19,420
Share-based compensation (shares)	[3],[4]			0
Share-based compensation and tax benefit	[3],[4]	1,144		$ 0		1,144
Treasury stock activities										(25)	25
Ending Balances (shares) at Sep. 30, 2020	[1],[2]			16,696,492
Ending Balances at Sep. 30, 2020		$ 616,690	[1]	$ 8,126	[1]	283,836		328,357	(3,629)	5,634	(5,634)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares Held In Trust For Deferred Compensation Plan		104,119
Preferred Stock, Shares Authorized		2,000,000
Preferred Stock, Par or Stated Value Per Share		$ 0.01
Shares Held In Trust For Deferred Compensation Plan		105,087
Common Stock, Dividends, Per Share, Declared		$ 1.400
Beginning Balances (shares) at Dec. 31, 2020	[1],[2]			17,461,841
Beginning Balances at Dec. 31, 2020		$ 697,085		$ 8,499	[1],[2]	348,482		342,969	(2,865)	5,679	(5,679)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income		60,754						60,754
Other comprehensive income (loss)		5,304							5,304
Other Comprehensive Income (Loss), Net of Tax		5,304
Dividend declared		(24,826)						(24,826)
Retirement savings plan and dividend reinvestment plan (shares)				80,022
Dividend reinvestment plan		9,286		$ 39		9,247
Share-based compensation (shares)	[3],[4]			45,971
Share-based compensation and tax benefit	[3],[4]	3,359		$ 22		3,337
Treasury stock activities								0		1,507	(1,507)
Ending Balances (shares) at Sep. 30, 2021	[1],[2]			17,587,834
Ending Balances at Sep. 30, 2021		$ 750,962	[1]	$ 8,560	[1]	361,066		378,897	2,439	7,186	(7,186)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based Payment Arrangement, Shares Withheld for Tax Withholding Obligation		14,020
Common Stock, Dividends, Per Share, Declared		$ 0.4800
Beginning Balances (shares) at Jun. 30, 2021	[1],[2]			17,567,928
Beginning Balances at Jun. 30, 2021		$ 741,564	[1]	$ 8,550	[1]	357,520		374,936	558	7,203	(7,203)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income		12,475						12,475
Other comprehensive income (loss)		1,881							1,881
Other Comprehensive Income (Loss), Net of Tax		1,881
Dividend declared		(8,514)						(8,514)
Retirement savings plan and dividend reinvestment plan (shares)				19,906
Dividend reinvestment plan		2,451		$ 10		2,441
Share-based compensation (shares)	[3],[4]			0
Share-based compensation and tax benefit	[3],[4]	1,105		$ 0		1,105
Treasury stock activities		0								(17)	17
Ending Balances (shares) at Sep. 30, 2021	[1],[2]			17,587,834
Ending Balances at Sep. 30, 2021		$ 750,962	[1]	$ 8,560	[1]	$ 361,066		$ 378,897	$ 2,439	$ 7,186	$ (7,186)
Preferred Stock, Shares Authorized		2,000,000
Preferred Stock, Par or Stated Value Per Share		$ 0.01
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares Held In Trust For Deferred Compensation Plan		114,016

[1] 2,000,000 shares of preferred stock at $0.01 par value have been authorized. No shares have been issued or are outstanding; accordingly, no information has been included in the statements of stockholders’ equity.

[2] Includes 114,016, 105,087, 104,119, and 95,329 shares at September 30, 2021, December 31, 2020, September 30, 2020 and December 31, 2019, respectively, held in a Rabbi Trust related to our Non-Qualified Deferred Compensation Plan.

[3] Includes amounts for shares issued for directors’ compensation.

[4] The shares issued under the SICP are net of shares withheld for employee taxes. For the nine months ended September 30, 2021 and 2020, we withheld 14,020 and 10,319 shares, respectively, for employee taxes.