Loans (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Jun. 30, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Dec. 31, 2010
Loan balances
Total loans	$ 802,672		$ 785,268
Allowance for loan losses	(21,489)	(21,931)	(21,257)	(22,687)	(21,749)	(21,768)
Net loans	781,183		764,011
Commercial and Agriculture [Member]
Loan balances
Total loans	84,848		86,395
Allowance for loan losses	(2,569)	(2,537)	(2,876)	(3,949)	(2,821)	(3,639)
Commercial real estate [Member]
Loan balances
Total loans	405,535		371,852
Allowance for loan losses	(11,227)	(11,701)	(10,571)	(10,453)	(10,713)	(9,827)
Real estate - mortgage [Member]
Loan balances
Total loans	256,840		274,995
Allowance for loan losses	(5,959)	(6,379)	(5,796)	(5,953)	(6,184)	(4,569)
Real estate - construction [Member]
Loan balances
Total loans	45,405		39,790
Allowance for loan losses	(1,065)	(1,095)	(974)	(1,211)	(1,196)	(2,139)
Consumer [Member]
Loan balances
Total loans	10,044		12,236
Allowance for loan losses	$ (253)	$ (262)	$ (719)	$ (634)	$ (670)	$ (726)