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		$ 0.3250
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		26,854
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)		(1,694)						(1,694)
Dividend declared		(5,380)					(5,380)
Retirement savings plan and dividend reinvestment plan (shares)				0
Dividend reinvestment plan		(1)		$ 0		(1)
Share-based compensation (shares)	[3],[4]			19,350
Share-based compensation and tax benefit	[3],[4]	666		$ 9		657
Treasury stock activities		0							178	(178)
Ending Balances (shares) at Mar. 31, 2018	[2]			16,363,792
Ending Balances at Mar. 31, 2018		505,241	[2]	$ 7,964	[2]	254,126	250,024	(6,873)	3,573	(3,573)
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		33,241
Tax Cuts and Jobs Act, Reclassification from AOCI to Retained Earnings, Tax Effect								(907)
Other comprehensive income (loss)		(539)
Ending Balances (shares) at Jun. 30, 2018	[1],[2]			16,378,545
Ending Balances at Jun. 30, 2018		$ 507,986	[2]	$ 7,971	[2]	255,356	250,377	(5,718)	3,782	(3,782)
Common Stock, Dividends, Per Share, Declared		$ 0.3700
Beginning Balances (shares) at Mar. 31, 2018	[2]			16,363,792
Beginning Balances at Mar. 31, 2018		$ 505,241	[2]	$ 7,964	[2]	254,126	250,024	(6,873)	3,573	(3,573)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income		6,387					6,387
Other comprehensive income (loss)		1,155						1,155
Dividend declared		(6,034)					(6,034)
Dividend reinvestment plan		(1)				(1)
Share-based compensation (shares)	[3],[4]			14,753
Share-based compensation and tax benefit	[3],[4]	1,238		$ 7		1,231
Treasury stock activities									209	(209)
Ending Balances (shares) at Jun. 30, 2018	[1],[2]			16,378,545
Ending Balances at Jun. 30, 2018		$ 507,986	[2]	$ 7,971	[2]	255,356	250,377	(5,718)	3,782	(3,782)
Preferred Stock, Shares Authorized		2,000,000
Preferred Stock, Par or Stated Value Per Share		$ 0.01
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	[2]	$ 7,971	[2]	255,651	261,530	(6,713)	3,854	(3,854)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income		28,664					28,664
Prior Period Reclassification Adjustment							115	(115)
Other comprehensive income (loss)		3,089						3,089
Dividend declared		(6,198)					(6,198)
Stock Issued During Period, Shares, Dividend Reinvestment Plan				0
Stock Issued During Period, Value, Dividend Reinvestment Plan		(1)		$ 0		(1)
Share-based compensation (shares)	[3],[4]			18,472
Share-based compensation and tax benefit	[3],[4]	(334)		$ 9		(343)
Treasury stock activities		0							522	(522)
Ending Balances (shares) at Mar. 31, 2019	[2]			16,397,017
Ending Balances at Mar. 31, 2019		543,659	[2]	$ 7,980	[2]	255,307	284,111	(3,739)	4,376	(4,376)
Beginning Balances (shares) at Dec. 31, 2018	[1],[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		36,968
Prior Period Reclassification Adjustment								(115)
Other comprehensive income (loss)		1,081
Ending Balances (shares) at Jun. 30, 2019	[1],[2]			16,403,776
Ending Balances at Jun. 30, 2019		$ 544,384	[2]	$ 7,984	[2]	256,385	285,762	(5,747)	4,694	(4,694)
Common Stock, Dividends, Per Share, Declared		$ 0.4050
Beginning Balances (shares) at Mar. 31, 2019	[2]			16,397,017
Beginning Balances at Mar. 31, 2019		$ 543,659	[2]	$ 7,980	[2]	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)
Dividend declared		(6,653)					(6,653)
Stock Issued During Period, Value, Dividend Reinvestment Plan		(1)				(1)
Share-based compensation (shares)	[3],[4]			6,759
Share-based compensation and tax benefit	[3],[4]	1,083		$ 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	[2]	$ 7,984	[2]	$ 256,385	$ 285,762	$ (5,747)	$ 4,694	$ (4,694)
Preferred Stock, Shares Authorized		2,000,000
Preferred Stock, Par or Stated Value Per Share		$ 0.01

[1] Includes 105,409 shares at June 30, 2019, 97,053 shares at December 31, 2018, 96,204 shares at June 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 three months ended June 30, 2018, we withheld 6,482 shares for employee taxes. We did not withhold any shares for employee taxes for the three months ended June 30, 2019. For the six months ended June 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.