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]
Common Stock, Dividends, Per Share, Declared		$ 1.0650
Beginning Balances (shares) at Dec. 31, 2017	[1],[2]			16,344,442
Beginning Balances at Dec. 31, 2017		$ 486,294	[2]	$ 7,955	[2]	$ 253,470	$ 229,141	$ (4,272)	$ 3,395	$ (3,395)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income		38,779					38,779
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification		(1,498)					(1,498)
Tax Cuts and Jobs Act, Reclassification from AOCI to Retained Earnings, Tax Effect		0					907	(907)
Other comprehensive income (loss)		192						192
Other Comprehensive Income (Loss), Net of Tax		192
Dividend declared		(17,524)					17,524
Retirement savings plan and dividend reinvestment plan (shares)				0
Dividend reinvestment plan		(2)		$ 0		(2)
Share-based compensation (shares)	[3],[4]			34,103
Share-based compensation and tax benefit	[3],[4]	2,057		$ 16		2,041
Treasury stock activities		0							423	(423)
Ending Balances (shares) at Sep. 30, 2018	[1],[2]			16,378,545
Ending Balances at Sep. 30, 2018		$ 508,298	[2]	$ 7,971	[2]	255,509	249,805	(4,987)	3,818	(3,818)
Common Stock, Dividends, Per Share, Declared		$ 0.3700
Beginning Balances (shares) at Jun. 30, 2018	[1],[2]			16,378,545
Beginning Balances at Jun. 30, 2018		$ 507,987	[2]	$ 7,971	[2]	255,356	250,377	(5,717)	3,782	(3,782)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income		5,538					5,538
Other comprehensive income (loss)		730						730
Other Comprehensive Income (Loss), Net of Tax		730
Dividend declared		(6,110)					(6,110)
Dividend reinvestment plan		0
Share-based compensation and tax benefit	[3],[4]	153				153
Treasury stock activities									36	(36)
Ending Balances (shares) at Sep. 30, 2018	[1],[2]			16,378,545
Ending Balances at Sep. 30, 2018		$ 508,298	[2]	$ 7,971	[2]	255,509	249,805	(4,987)	3,818	(3,818)
Preferred Stock, Shares Authorized		2,000,000
Preferred Stock, Par or Stated Value Per Share		$ 0.01
Common Stock, Dividends, Per Share, Declared		$ 1.1800
Beginning Balances (shares) at Dec. 31, 2018	[2]			16,378,545
Beginning Balances at Dec. 31, 2018		$ 518,439	[2]	$ 7,971	[2]	255,651	261,530	(6,713)	3,854	(3,854)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income		42,589					42,589
Prior Period Reclassification Adjustment							115	(115)
Other comprehensive income (loss)		1,505						1,425
Other Comprehensive Income (Loss), Net of Tax		1,425
Dividend declared		(19,540)					19,540
Retirement savings plan and dividend reinvestment plan (shares)				0
Dividend reinvestment plan		(3)		$ 0		(3)
Share-based compensation (shares)				25,231
Share-based compensation and tax benefit	[3],[4]	1,801		$ 13		1,788
Treasury stock activities		0							651	(651)
Ending Balances (shares) at Sep. 30, 2019	[2]			16,403,776
Ending Balances at Sep. 30, 2019		$ 544,711	[2]	$ 7,984	[2]	257,436	284,694	(5,403)	4,505	(4,505)
Common Stock, Dividends, Per Share, Declared		$ 0.4050
Beginning Balances (shares) at Jun. 30, 2019	[2]			16,403,776
Beginning Balances at Jun. 30, 2019		$ 544,384	[2]	$ 7,984	[2]	256,385	285,762	(5,747)	4,694	(4,694)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income		5,621					5,621
Other comprehensive income (loss)		424						344
Other Comprehensive Income (Loss), Net of Tax		344
Dividend declared		(6,689)					6,689
Retirement savings plan and dividend reinvestment plan (shares)				0
Dividend reinvestment plan		(1)		$ 0		(1)
Share-based compensation and tax benefit	[3],[4]	1,052		$ 0		1,052
Treasury stock activities		0							(189)	189
Ending Balances (shares) at Sep. 30, 2019	[2]			16,403,776
Ending Balances at Sep. 30, 2019		$ 544,711	[2]	$ 7,984	[2]	$ 257,436	$ 284,694	$ (5,403)	$ 4,505	$ (4,505)
Preferred Stock, Shares Authorized		2,000,000
Preferred Stock, Par or Stated Value Per Share		$ 0.01

[1] Includes 94,923 shares at September 30, 2019, 97,053 shares at December 31, 2018, 96,622 shares at September 30, 2018 and 90,961 shares at December 31, 2017, respectively, held in a Rabbi Trust related to our Non-Qualified Deferred Compensation Plan.

[2] 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.

[3] The shares issued under the SICP are net of shares withheld for employee taxes. For the nine months ended September 30, 2019 and 2018, we withheld 7,635 and 16,918 shares, respectively, for employee taxes.

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