Financial Instruments with Off-Balance-Sheet Risk (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Commitments to originate 1-4 family mortgages [Member]
Financial instruments with off-balance-sheet risk
Financial instruments with off-balance-sheet risk	$ 13,580	$ 12,638
Standby and commercial letters of credit [Member]
Financial instruments with off-balance-sheet risk
Financial instruments with off-balance-sheet risk	8,411	4,645
Unused lines of Credit [Member]
Financial instruments with off-balance-sheet risk
Financial instruments with off-balance-sheet risk	217,246	195,181
Unadvanced portions of construction loans [Member]
Financial instruments with off-balance-sheet risk
Financial instruments with off-balance-sheet risk	17,609	16,819
Unadvanced portions of other loans [Member]
Financial instruments with off-balance-sheet risk
Financial instruments with off-balance-sheet risk	$ 4,872	$ 4,605