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]
Beginning Balances (shares) at Dec. 31, 2014	[1]		14,588,711
Beginning Balances at Dec. 31, 2014		$ 300,322	$ 7,100	$ 156,581	$ 142,317	$ (5,676)	$ 1,258	$ (1,258)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income		41,140			41,140
Other comprehensive loss		(164)				(164)
Dividend declared ($1.1325 per share)		(17,222)			(17,222)
Retirement savings plan and dividend reinvestment plan (shares)			43,275
Retirement savings plan and dividend reinvestment plan		2,235	$ 21	2,214
Common stock issued in acquisition (shares)			592,970
Common stock issued in acquisition		30,165	$ 289	29,876
Share-based compensation (shares)	[1],[2],[3]		45,703
Share-based compensation and tax benefit	[2],[3]	1,662	$ 22	1,640
Treasury stock activities		0					625	(625)
Ending Balances (shares) at Dec. 31, 2015	[1]		15,270,659
Ending Balances at Dec. 31, 2015		358,138	$ 7,432	190,311	166,235	(5,840)	1,883	(1,883)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income		20,367			20,367
Other comprehensive loss		89				89
Dividend declared ($0.2875 per share) and dividend reinvestment plan (shares)			6,787
Dividend declared ($0.2875 per share) and dividend reinvestment plan		(4,057)	$ 3	377	(4,437)
Share-based compensation (shares)	[1],[2],[3]		27,522
Share-based compensation and tax benefit	[2],[3]	(285)	$ 14	(299)
Treasury stock activities		0					338	(338)
Ending Balances (shares) at Mar. 31, 2016	[1]		15,304,968
Ending Balances at Mar. 31, 2016		$ 374,252	$ 7,449	$ 190,389	$ 182,165	$ (5,751)	$ 2,221	$ (2,221)

[1] Includes 75,959 and 70,631 shares at March 31, 2016 and December 31, 2015, respectively, held in a Rabbi Trust related to our Deferred Compensation Plan.

[2] Includes amounts for shares issued for Directors’ compensation.

[3] The shares issued under the SICP are net of shares withheld for employee taxes. For the three months ended March 31, 2016, and for the year ended December 31, 2015, we withheld 12,031 and 12,620 shares, respectively, for taxes.