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		97,053
Common Stock, Dividends, Per Share, Declared		$ 0.3700
Beginning Balances (shares) at Dec. 31, 2018	[1],[2]			16,378,545
Beginning Balances at Dec. 31, 2018		$ 518,439		$ 7,971	[1]	$ 255,651		$ 261,530	$ (6,713)	$ 3,854	$ (3,854)
Ending Balances (shares) at Mar. 31, 2019	[1],[2]			16,397,017
Ending Balances at Mar. 31, 2019		$ 543,659	[1]	$ 7,980	[1]	255,307		284,111	(3,739)	4,376	(4,376)
Common Stock, Dividends, Per Share, Declared		$ 0.7750
Beginning Balances (shares) at Dec. 31, 2018	[1],[2]			16,378,545
Beginning Balances at Dec. 31, 2018		$ 518,439		$ 7,971	[1]	255,651		261,530	(6,713)	3,854	(3,854)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income		36,968						36,968
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification		0						115	(115)
Tax Cuts and Jobs Act, Reclassification from AOCI to Retained Earnings, Tax Effect									(115)
Other comprehensive income (loss)		1,081							1,081
Other Comprehensive Income (Loss), Net of Tax		1,081
Dividend declared		(12,851)						(12,851)
Retirement savings plan and dividend reinvestment plan (shares)				0
Dividend reinvestment plan		(2)		$ 0		(2)
Share-based compensation (shares)				25,231
Share-based compensation and tax benefit		749	[3],[4]	$ 13		736	[3],[4]
Treasury stock activities		0								840	(840)
Ending Balances (shares) at Jun. 30, 2019	[1],[2]			16,403,776
Ending Balances at Jun. 30, 2019		$ 544,384	[1]	$ 7,984	[1]	256,385		285,762	(5,747)	4,694	(4,694)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based Payment Arrangement, Shares Withheld for Tax Withholding Obligation		7,635
Common Stock, Dividends, Per Share, Declared		$ 0.4050
Beginning Balances (shares) at Mar. 31, 2019	[1],[2]			16,397,017
Beginning Balances at Mar. 31, 2019		$ 543,659	[1]	$ 7,980	[1]	255,307		284,111	(3,739)	4,376	(4,376)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income		8,304						8,304
Other comprehensive income (loss)		(2,008)							(2,008)
Other Comprehensive Income (Loss), Net of Tax		(2,008)
Dividend declared		(6,653)						6,653
Dividend reinvestment plan		(1)				(1)
Share-based compensation (shares)	[3],[4]			6,759
Share-based compensation and tax benefit		1,083	[3],[4]	$ 4	[3],[4]	1,079
Treasury stock activities										318	(318)
Ending Balances (shares) at Jun. 30, 2019	[1],[2]			16,403,776
Ending Balances at Jun. 30, 2019		$ 544,384	[1]	$ 7,984	[1]	256,385		285,762	(5,747)	4,694	(4,694)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares Held In Trust For Deferred Compensation Plan		105,409
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		95,329
Common Stock, Dividends, Per Share, Declared		$ 0.4050
Beginning Balances (shares) at Dec. 31, 2019	[1]			16,403,776
Beginning Balances at Dec. 31, 2019		$ 561,577	[1]	$ 7,984	[1]	259,253		300,607	(6,267)	4,543	(4,543)
Ending Balances (shares) at Mar. 31, 2020	[1]			16,433,105
Ending Balances at Mar. 31, 2020		$ 584,129	[1]	$ 7,998	[1]	259,521		322,804	(6,194)	5,468	(5,468)
Common Stock, Dividends, Per Share, Declared		$ 0.8450
Beginning Balances (shares) at Dec. 31, 2019	[1]			16,403,776
Beginning Balances at Dec. 31, 2019		$ 561,577	[1]	$ 7,984	[1]	259,253		300,607	(6,267)	4,543	(4,543)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income		39,886						39,886
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification								(30)
Other comprehensive income (loss)		1,805							1,805
Other Comprehensive Income (Loss), Net of Tax		1,805
Dividend declared		(14,009)						14,009
Retirement savings plan and dividend reinvestment plan (shares)				25,576
Dividend reinvestment plan		2,286		$ 13		2,273
Share-based compensation (shares)				34,456
Share-based compensation and tax benefit	[3],[4]	1,762		$ 16		1,746
Treasury stock activities		0								1,116	(1,116)
Ending Balances (shares) at Jun. 30, 2020	[1]			16,463,808
Ending 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]
Share-based Payment Arrangement, Shares Withheld for Tax Withholding Obligation		10,319
Common Stock, Dividends, Per Share, Declared		$ 0.4400
Beginning Balances (shares) at Mar. 31, 2020	[1]			16,433,105
Beginning Balances at Mar. 31, 2020		$ 584,129	[1]	$ 7,998	[1]	259,521		322,804	(6,194)	5,468	(5,468)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income		10,956						10,956
Other comprehensive income (loss)		1,732							1,732
Other Comprehensive Income (Loss), Net of Tax		1,732
Dividend declared		(7,306)						7,306
Retirement savings plan and dividend reinvestment plan (shares)				21,833
Dividend reinvestment plan		1,932		$ 11		1,921
Share-based compensation (shares)				8,870
Share-based compensation and tax benefit		1,834	[3],[4]	$ 4		1,830	[3],[4]
Treasury stock activities		0								191	(191)
Ending Balances (shares) at Jun. 30, 2020	[1]			16,463,808
Ending Balances at Jun. 30, 2020		$ 593,277	[1]	$ 8,013	[1]	$ 263,272		$ 326,454	$ (4,462)	$ 5,659	$ (5,659)
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		107,141

[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 107,141 shares at June 30, 2020, 95,329 shares at December 31, 2019, 105,409 shares at June 30, 2019 and 97,053 shares at December 31, 2018, respectively, held in a Rabbi Trust related to our Non-Qualified Deferred Compensation Plan.

[3] The shares issued under the SICP are net of shares withheld for employee taxes. For the six months ended June 30, 2020 and 2019, we withheld 10,319 and 7,635 shares, respectively, for employee taxes.

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