Loans, Troubled Debt Restructurings Segregated by Class (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		12 Months Ended
	Mar. 31, 2013 Loan	Mar. 31, 2012 Loan	Dec. 31, 2012 Loan
Financing Receivable, Modifications [Line Items]
Number of troubled debt restructuring that occurred during the period	17	4	40
Post-modification outstanding balance	$ 8,300	$ 1,713	$ 8,687
Net charge-offs resulting from modification	0	0	0
Defaulted restructured loans, number of loans	5	5
Defaulted Restructured loans, recorded investment	1,002	402
Commercial Construction [Member]
Financing Receivable, Modifications [Line Items]
Number of troubled debt restructuring that occurred during the period	3	0	5
Post-modification outstanding balance	2,110	0	557
Net charge-offs resulting from modification	0	0	0
Defaulted restructured loans, number of loans	2	0
Defaulted Restructured loans, recorded investment	328	0
Commercial Secured by Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Number of troubled debt restructuring that occurred during the period	5	3	11
Post-modification outstanding balance	605	1,665	4,506
Net charge-offs resulting from modification	0	0	0
Defaulted restructured loans, number of loans	2	3
Defaulted Restructured loans, recorded investment	662	370
Commercial Other [Member]
Financing Receivable, Modifications [Line Items]
Number of troubled debt restructuring that occurred during the period	9	1	23
Post-modification outstanding balance	5,585	48	3,233
Net charge-offs resulting from modification	0	0	0
Defaulted restructured loans, number of loans	1	2
Defaulted Restructured loans, recorded investment	12	32
Real Estate Mortgage [Member]
Financing Receivable, Modifications [Line Items]
Number of troubled debt restructuring that occurred during the period			1
Post-modification outstanding balance			391
Net charge-offs resulting from modification			$ 0