Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Assets
Cash and due from banks	$ 66,893	$ 53,646
Federal funds sold and interest-bearing deposits in other banks	66,596	98,637
Total cash and cash equivalents	133,489	152,283
Short-term investments	9,611	17,367
Securities available-for-sale, amortized cost $495,931 and $1,414,595, respectively	494,901	1,434,801
Securities held-to-maturity, fair value $1,371,118 and $281,924, respectively	1,374,712	275,507
Federal Home Loan Bank of Boston stock, at cost	17,692	15,146
Loans, net:
Commercial and industrial	87,468	88,475
Construction and land development	32,750	38,618
Commercial real estate	666,166	576,465
Residential real estate	309,291	281,857
Home equity	126,645	118,923
Consumer and other	8,728	7,450
Total loans, net	1,231,048	1,111,788
Less: allowance for loan losses	21,250	19,197
Net loans	1,209,798	1,092,591
Bank premises and equipment	23,355	23,899
Accrued interest receivable	6,076	5,811
Goodwill	2,714	2,714
Other assets	88,735	66,090
Total assets	3,361,083	3,086,209
Deposits:
Demand deposits	475,644	438,429
Savings and NOW deposits	990,637	933,316
Money Market Accounts	870,298	653,345
Time deposits	351,550	419,983
Total deposits	2,688,129	2,445,073
Securities sold under agreements to repurchase	185,160	191,390
Other borrowed funds	241,144	195,144
Subordinated debentures	36,083	36,083
Due to broker	3,086
Other liabilities	41,161	38,529
Total liabilities	3,194,763	2,906,219
Stockholders' Equity
Preferred stock - $1.00 par value; 100,000 shares authorized; no shares issued and outstanding
Additional paid-in capital	11,932	11,891
Retained earnings	176,271	162,892
Stockholders' equity before adjustment of accumulated other comprehensive (income) loss	193,759	180,337
Unrealized (losses) gains on securities available-for-sale, net of taxes	(639)	12,330
Unrealized losses on securities transferred to held-to-maturity, net of taxes	(14,643)
Pension liability, net of taxes	(12,157)	(12,677)
Total accumulated other comprehensive loss, net of taxes	(27,439)	(347)
Total stockholders' equity	166,320	179,990
Total liabilities and stockholders' equity	3,361,083	3,086,209
Class A Common Stock [Member]
Stockholders' Equity
Common stock value	3,578	3,568
Total stockholders' equity	3,578	3,568
Class B Common Stock [Member]
Stockholders' Equity
Common stock value	1,978	1,986
Total stockholders' equity	$ 1,978	$ 1,986