Consolidated Statements of Stockholders' Equity - 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]
Beginning Balances at Dec. 31, 2015		$ 358,138	[1]	$ 7,432		$ 190,311		$ 166,235	$ (5,840)	$ 1,883		$ (1,883)
Beginning Balances, shares at Dec. 31, 2015	[1],[2]			15,270,659
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income		44,675						44,675
Other comprehensive loss		962							962
Dividends		(18,848)						(18,848)
Proceeds from issuance of common stock, net of expenses	[3]	$ 57,360		$ 467		56,893
Stock Issued During Period, Shares, New Issues		960,488		960,488	[3]
Stock Issued During The Period Value Retirement Savings Plan And Dividend Reinvestment Plan		$ 2,242		$ 17		2,225
Stock Issued During The Period Shares Retirement Savings Plan And Dividend Reinvestment Plan				36,253
Share-based compensation	[4],[5]	1,557		$ 19		1,538
Share-based compensation, shares	[4],[5]			36,099
Treasury stock activities	[1]									533		(533)
Ending Balances at Dec. 31, 2016		446,086	[1]	$ 7,935		250,967		192,062	(4,878)	2,416		(2,416)
Ending Balances, shares at Dec. 31, 2016	[1],[2]			16,303,499
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income		58,124						58,124
Other comprehensive loss		606							606
Dividends		(21,045)						(21,045)
Proceeds from issuance of common stock, net of expenses	[3]	(10)		$ 0		(10)
Stock Issued During Period, Shares, New Issues	[3]			0
Stock Issued During The Period Value Retirement Savings Plan And Dividend Reinvestment Plan		735		$ 5		730
Stock Issued During The Period Shares Retirement Savings Plan And Dividend Reinvestment Plan				10,771
Share-based compensation	[4],[5]	1,798		$ 15		1,783
Share-based compensation, shares	[4],[5]			30,172
Treasury stock activities		0								979	[1]	(979)	[1]
Ending Balances at Dec. 31, 2017		486,294	[1]	$ 7,955		253,470		229,141	(4,272)	3,395		(3,395)
Ending Balances, shares at Dec. 31, 2017	[1],[2]			16,344,442
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income		56,580						56,580
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification		(1,498)
Tax Cuts and Jobs Act, Reclassification from AOCI to Retained Earnings, Tax Effect		(907)						907	(907)
Other comprehensive loss		(1,534)							(1,534)
Dividends		(23,600)						(23,600)
Stock Issued During Period, Shares, Dividend Reinvestment Plan				0
Stock Issued During Period, Value, Dividend Reinvestment Plan		(3)		$ 0		(3)
Proceeds from issuance of common stock, net of expenses		0
Share-based compensation		2,200	[4],[5]	$ 16		2,184	[4],[5]
Share-based compensation, shares	[4],[5]			34,103
Treasury stock activities										459		(459)
Ending Balances at Dec. 31, 2018		$ 518,439	[1]	$ 7,971		$ 255,651		$ 261,530	$ (6,713)	$ 3,854		$ (3,854)
Ending Balances, shares at Dec. 31, 2018	[1],[2]			16,378,545

[1] Includes 97,053, 90,961 and 76,745 shares at December 31, 2018, 2017 and 2016, 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 per share have been authorized. No shares have been issued or are outstanding; accordingly, no information has been included in the Statements of Stockholders’ Equity.

[3] On September 22, 2016, we completed a public offering of 960,488 shares of our common stock at a price per share of $62.26. The net proceeds from the sale of common stock, after deducting underwriting commissions and expenses, were approximately $57.4 million.

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

[5] The shares issued under the SICP are net of shares withheld for employee taxes. For 2018, 2017 and 2016, we withheld 10,436, 10,269 and 12,031 shares, respectively, for taxes.