Financial Instruments with Off-Balance Sheet Risk and Derivative Transactions (Details 2) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Company's contractual commitments due to letters of credit
Total letters of credit	$ 9,986	$ 10,646
Fixed
Company's contractual commitments due to letters of credit
Total letters of credit	1,840	1,875
Variable
Company's contractual commitments due to letters of credit
Total letters of credit	8,146	8,771
Letters of credit: Borrower
Company's contractual commitments due to letters of credit
Total letters of credit	8,657	9,281
Letters of credit: Borrower | Fixed
Company's contractual commitments due to letters of credit
Total letters of credit	1,600	1,635
Letters of credit: Borrower | Variable
Company's contractual commitments due to letters of credit
Total letters of credit	7,057	7,646
Letters of credit: Borrower | Financial standby
Company's contractual commitments due to letters of credit
Total letters of credit	3,493	3,383
Letters of credit: Borrower | Financial standby | Fixed
Company's contractual commitments due to letters of credit
Total letters of credit	5	5
Letters of credit: Borrower | Financial standby | Variable
Company's contractual commitments due to letters of credit
Total letters of credit	3,488	3,378
Letters of credit: Borrower | Commercial standby
Company's contractual commitments due to letters of credit
Total letters of credit	51	51
Letters of credit: Borrower | Commercial standby | Variable
Company's contractual commitments due to letters of credit
Total letters of credit	51	51
Letters of credit: Borrower | Performance standby
Company's contractual commitments due to letters of credit
Total letters of credit	5,113	5,847
Letters of credit: Borrower | Performance standby | Fixed
Company's contractual commitments due to letters of credit
Total letters of credit	1,595	1,630
Letters of credit: Borrower | Performance standby | Variable
Company's contractual commitments due to letters of credit
Total letters of credit	3,518	4,217
Letters of credit: Non-borrower
Company's contractual commitments due to letters of credit
Total letters of credit	1,329	1,365
Letters of credit: Non-borrower | Fixed
Company's contractual commitments due to letters of credit
Total letters of credit	240	240
Letters of credit: Non-borrower | Variable
Company's contractual commitments due to letters of credit
Total letters of credit	1,089	1,125
Letters of credit: Non-borrower | Performance standby
Company's contractual commitments due to letters of credit
Total letters of credit	1,329	1,365
Letters of credit: Non-borrower | Performance standby | Fixed
Company's contractual commitments due to letters of credit
Total letters of credit	240	240
Letters of credit: Non-borrower | Performance standby | Variable
Company's contractual commitments due to letters of credit
Total letters of credit	$ 1,089	$ 1,125