Financial Instruments with Off-Balance Sheet Risk and Derivative Transactions (Details 2) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Company's contractual commitments due to letters of credit
Total letters of credit	$ 11,426	$ 14,640
Financial standby letters of credit
Company's contractual commitments due to letters of credit
Total letters of credit	3,932	3,387
Performance standby letters of credit
Company's contractual commitments due to letters of credit
Total letters of credit	7,443	10,878
Commercial letters of credit
Company's contractual commitments due to letters of credit
Total letters of credit	51	375
Commitments to extend credit: borrowers
Company's contractual commitments due to letters of credit
Total letters of credit	9,664	11,766
Commitments to extend credit: borrowers | Financial standby letters of credit
Company's contractual commitments due to letters of credit
Total letters of credit	3,382	2,837
Commitments to extend credit: borrowers | Performance standby letters of credit
Company's contractual commitments due to letters of credit
Total letters of credit	6,231	8,554
Commitments to extend credit: borrowers | Commercial letters of credit
Company's contractual commitments due to letters of credit
Total letters of credit	51	375
Commitments to extend credit: other
Company's contractual commitments due to letters of credit
Total letters of credit	1,762	2,874
Commitments to extend credit: other | Financial standby letters of credit
Company's contractual commitments due to letters of credit
Total letters of credit	550	550
Commitments to extend credit: other | Performance standby letters of credit
Company's contractual commitments due to letters of credit
Total letters of credit	$ 1,212	$ 2,324