CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY (USD $) In Thousands, except Share data, unless otherwise specified	Total	Common Stock	Treasury Stock	Additional Paid-In Capital	Accumulated Earnings	Accumulated Other Comprehensive Income
Beginning Balance at Dec. 31, 2010	$ 328,721	$ 191	$ (12,102)	$ 180,884	$ 159,483	$ 265
Beginning Balance, Shares at Dec. 31, 2010		19,060,649	(708,608)
Comprehensive income:
Net income	24,181				24,181
Other comprehensive income:
Change in unrealized gains (losses), net of tax	1,986					1,986
Change in deferred tax valuation allowance	(36)					(36)
Comprehensive income	26,131
Common stock issued upon exercise of options	3,339	3		3,336
Common stock issued upon exercise of options, Shares	338,350	338,350
Restricted common stock issued	210			210
Restricted common stock issued, Shares		9,513
Share-based compensation	261			261
Tax benefit of share-based compensation	1,043			1,043
Purchase of treasury stock	(10,268)		(10,268)
Purchase of treasury stock, Shares			(549,642)
Ending Balance at Dec. 31, 2011	349,437	194	(22,370)	185,734	183,664	2,215
Ending Balance, Shares at Dec. 31, 2011		19,408,512	(1,258,250)
Comprehensive income:
Net income	29,353				29,353
Other comprehensive income:
Change in unrealized gains (losses), net of tax	764					764
Change in deferred tax valuation allowance
Comprehensive income	30,117
Common stock issued upon exercise of options	781	1		780
Common stock issued upon exercise of options, Shares	86,800	86,800
Restricted common stock issued	240			240
Restricted common stock issued, Shares		18,164
Share-based compensation	226			226
Tax benefit of share-based compensation	421			421
Ending Balance at Dec. 31, 2012	381,222	195	(22,370)	187,401	213,017	2,979
Ending Balance, Shares at Dec. 31, 2012	18,255,226	19,513,476	(1,258,250)
Comprehensive income:
Net income	43,637				43,637
Other comprehensive income:
Change in unrealized gains (losses), net of tax	(7,274)					(7,274)
Change in deferred tax valuation allowance
Comprehensive income	36,363
Common stock issued upon exercise of options	2,344	3		2,341
Common stock issued upon exercise of options, Shares	256,300	256,300
Restricted common stock issued	557			557
Restricted common stock issued, Shares		85,654
Share-based compensation	214			214
Tax benefit of share-based compensation	2,024			2,024
Dividends to shareholders	(5,910)				(5,910)
Ending Balance at Dec. 31, 2013	$ 416,814	$ 198	$ (22,370)	$ 192,537	$ 250,744	$ (4,295)
Ending Balance, Shares at Dec. 31, 2013	18,597,180	19,855,430	(1,258,250)