Restatement Of Consolidated Financial Statements (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Sep. 30, 2012 As Previously Reported [Member]	Jun. 30, 2012 As Previously Reported [Member]	Mar. 31, 2012 As Previously Reported [Member]	Dec. 31, 2011 As Previously Reported [Member]	Sep. 30, 2011 As Previously Reported [Member]	Jun. 30, 2011 As Previously Reported [Member]	Mar. 31, 2011 As Previously Reported [Member]	Dec. 31, 2010 As Previously Reported [Member]	Sep. 30, 2010 As Previously Reported [Member]	Jun. 30, 2010 As Previously Reported [Member]	Mar. 31, 2010 As Previously Reported [Member]	Dec. 31, 2009 As Previously Reported [Member]	Sep. 30, 2012 As Restated [Member]	Jun. 30, 2012 As Restated [Member]	Mar. 31, 2012 As Restated [Member]	Dec. 31, 2011 As Restated [Member]	Sep. 30, 2011 As Restated [Member]	Jun. 30, 2011 As Restated [Member]	Mar. 31, 2011 As Restated [Member]	Dec. 31, 2010 As Restated [Member]	Sep. 30, 2010 As Restated [Member]	Jun. 30, 2010 As Restated [Member]	Mar. 31, 2010 As Restated [Member]	Dec. 31, 2009 As Restated [Member]	Sep. 30, 2012 Correction Of Deferred Tax [Member]	Jun. 30, 2012 Correction Of Deferred Tax [Member]	Mar. 31, 2012 Correction Of Deferred Tax [Member]	Dec. 31, 2011 Correction Of Deferred Tax [Member]	Sep. 30, 2011 Correction Of Deferred Tax [Member]	Jun. 30, 2011 Correction Of Deferred Tax [Member]	Mar. 31, 2011 Correction Of Deferred Tax [Member]	Dec. 31, 2010 Correction Of Deferred Tax [Member]	Sep. 30, 2010 Correction Of Deferred Tax [Member]	Jun. 30, 2010 Correction Of Deferred Tax [Member]	Mar. 31, 2010 Correction Of Deferred Tax [Member]	Dec. 31, 2009 Correction Of Deferred Tax [Member]
Long-term deferred income taxes				$ 1,575	$ 1,503	$ 1,431	$ 1,358	$ 2,412	$ 2,050	$ 1,999	$ 1,941	$ 3,925	$ 3,820	$ 3,650		$ 2,852	$ 2,780	$ 2,708	$ 2,635	$ 3,689	$ 3,327	$ 3,276	$ 3,218	$ 5,202	$ 5,097	$ 4,927		$ 1,277	$ 1,277	$ 1,277	$ 1,277	$ 1,277	$ 1,277	$ 1,277	$ 1,277	$ 1,277	$ 1,277	$ 1,277
Total liabilities	28,910	28,915		30,515	27,555	26,427	27,638	31,672	14,561	14,860	16,650	17,941	17,817	18,367	18,661	31,792	28,832	27,704	28,915	32,949	15,838	16,137	17,927	19,218	19,094	19,644	19,938	1,277	1,277	1,277	1,277	1,277	1,277	1,277	1,277	1,277	1,277	1,277	1,277
Retained earnings	13,628	29,364		23,544	26,034	27,833	30,641	34,008	37,128	38,800	39,356	40,901	40,941	41,370		22,267	24,757	26,556	29,364	32,731	35,851	37,523	38,079	39,624	39,664	40,093		(1,277)	(1,277)	(1,277)	(1,277)	(1,277)	(1,277)	(1,277)	(1,277)	(1,277)	(1,277)	(1,277)
Total shareholders' equity	$ 14,535	$ 24,876	$ 35,148	$ 23,781	$ 22,093	$ 23,617	$ 26,153	$ 31,883	$ 34,684	$ 35,919	$ 36,425	$ 37,690	$ 37,429	$ 37,720	$ 37,905	$ 22,504	$ 20,816	$ 22,340	$ 24,876	$ 30,606	$ 33,407	$ 34,642	$ 35,148	$ 36,413	$ 36,152	$ 36,443	$ 36,628	$ (1,277)	$ (1,277)	$ (1,277)	$ (1,277)	$ (1,277)	$ (1,277)	$ (1,277)	$ (1,277)	$ (1,277)	$ (1,277)	$ (1,277)	$ (1,277)