Loans (Details 2) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Balance in the recorded investment in loans and allowance for loan losses by portfolio segment and based on impairment method
Loans	$ 1,584,594	$ 1,544,845	$ 1,508,425
Balance: loans individually evaluated for impairment	29,329	22,139	17,270
Balance: loans collectively evaluated for impairment	1,555,265	1,522,706	1,491,155
Allowance for loan losses
Balance at the beginning of the period	29,745	25,543	20,000
Provision	11,500	12,600	11,469
Charge-offs	(10,498)	(9,121)	(6,766)
Recoveries	1,134	723	840
Balance at the end of the period	31,881	29,745	25,543
Balance: allowance for loans individually evaluated for impairment	3,617	2,561	1,814
Balance: allowance for loans collectively evaluated for impairment	28,264	27,184	23,729
Commercial and industrial
Balance in the recorded investment in loans and allowance for loan losses by portfolio segment and based on impairment method
Loans	426,930	393,729	343,956
Balance: loans individually evaluated for impairment	8,667	5,459	520
Balance: loans collectively evaluated for impairment	418,263	388,270	343,436
Allowance for loan losses
Balance at the beginning of the period	7,364	2,796	4,091
Provision	3,024	5,475	8
Charge-offs	(4,523)	(1,015)	(1,418)
Recoveries	84	108	115
Balance at the end of the period	5,949	7,364	2,796
Balance: allowance for loans individually evaluated for impairment	156	954	90
Balance: allowance for loans collectively evaluated for impairment	5,793	6,410	2,706
Construction and development
Balance in the recorded investment in loans and allowance for loan losses by portfolio segment and based on impairment method
Loans	131,253	147,637	159,482
Balance: loans individually evaluated for impairment	10,863	2,416	700
Balance: loans collectively evaluated for impairment	120,390	145,221	158,782
Allowance for loan losses
Balance at the beginning of the period	3,546	2,280	1,518
Provision	2,716	2,859	2,947
Charge-offs	(1,726)	(1,593)	(2,211)
Recoveries			26
Balance at the end of the period	4,536	3,546	2,280
Balance: allowance for loans individually evaluated for impairment	2,898	10
Balance: allowance for loans collectively evaluated for impairment	1,638	3,536	2,280
Real estate mortgage
Balance in the recorded investment in loans and allowance for loan losses by portfolio segment and based on impairment method
Loans	989,631	966,665	968,440
Balance: loans individually evaluated for impairment	9,795	14,170	15,955
Balance: loans collectively evaluated for impairment	979,836	952,495	952,485
Allowance for loan losses
Balance at the beginning of the period	11,182	12,272	6,513
Provision	6,308	4,592	8,046
Charge-offs	(3,451)	(5,840)	(2,450)
Recoveries	249	158	163
Balance at the end of the period	14,288	11,182	12,272
Balance: allowance for loans individually evaluated for impairment	563	1,597	1,724
Balance: allowance for loans collectively evaluated for impairment	13,725	9,585	10,548
Consumer
Balance in the recorded investment in loans and allowance for loan losses by portfolio segment and based on impairment method
Loans	36,780	36,814	36,547
Balance: loans individually evaluated for impairment	4	94	95
Balance: loans collectively evaluated for impairment	36,776	36,720	36,452
Allowance for loan losses
Balance at the beginning of the period	540	623	947
Provision	(181)	133	(173)
Charge-offs	(798)	(673)	(687)
Recoveries	801	457	536
Balance at the end of the period	362	540	623
Balance: allowance for loans collectively evaluated for impairment	362	540	623
Unallocated
Allowance for loan losses
Balance at the beginning of the period	7,113	7,572	6,931
Provision	(367)	(459)	641
Balance at the end of the period	6,746	7,113	7,572
Balance: allowance for loans collectively evaluated for impairment	$ 6,746	$ 7,113	$ 7,572