Consolidated Statements of Changes in Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	AOCI Attributable to Parent [Member]	Total
Balance at Dec. 31, 2013	$ 914	$ 46,873	$ 157,107	$ 1,662	$ 206,556
Balance (in Shares) at Dec. 31, 2013	9,141,767
Net income			17,555		17,555
Other comprehensive income (loss)				10,588	10,588
Repurchase of common stock		(121)			(121)
Repurchase of common stock (in Shares)	(2,902)
Common stock issued under stock compensation plans, including tax benefit	$ 4	870			874
Common stock issued under stock compensation plans, including tax benefit (in Shares)	41,780
Common stock issued under dividend reinvestment and stock purchase plan	$ 4	1,679			1,683
Common stock issued under dividend reinvestment and stock purchase plan (in Shares)	43,889
3-for-2 stock split	$ 462		(462)
3-for-2 stock split (in Shares)	4,612,267
Stock-based compensation		893			893
Cash dividends declared			(7,360)		(7,360)
Balance at Sep. 30, 2014	$ 1,384	50,194	166,840	12,250	230,668
Balance (in Shares) at Sep. 30, 2014	13,836,801
Balance at Dec. 31, 2014	$ 1,389	51,009	170,120	10,785	233,303
Balance (in Shares) at Dec. 31, 2014	13,887,134
Net income			19,272		19,272
Other comprehensive income (loss)				(974)	(974)
Repurchase of common stock	$ (1)	(286)			(287)
Repurchase of common stock (in Shares)	(12,227)
Common stock issued under stock compensation plans, including tax benefit	$ 7	741			748
Common stock issued under stock compensation plans, including tax benefit (in Shares)	76,183
Common stock issued under dividend reinvestment and stock purchase plan	$ 9	2,275			2,284
Common stock issued under dividend reinvestment and stock purchase plan (in Shares)	92,093
Stock-based compensation		1,053			1,053
Cash dividends declared			(8,119)		(8,119)
Balance at Sep. 30, 2015	$ 1,404	$ 54,792	$ 181,273	$ 9,811	$ 247,280
Balance (in Shares) at Sep. 30, 2015	14,043,183