Borrowings (Schedule of Other Borrowed Funds) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Debt Instrument [Line Items]
FHLBB advances less than 90 days	$ 11,039	$ 11,112
Total short-term borrowings	445,921us-gaap_ShortTermBorrowings	398,932us-gaap_ShortTermBorrowings	192,681us-gaap_ShortTermBorrowings
Total long-term borrowings	31,018us-gaap_LongTermDebt	31,126us-gaap_LongTermDebt
Total other borrowed funds	476,939us-gaap_DebtAndCapitalLeaseObligations	430,058us-gaap_DebtAndCapitalLeaseObligations
Short-term Debt [Member]
Debt Instrument [Line Items]
Securities Sold under Agreements to Repurchase	157,758	130,047
FHLBB advances less than 90 days	245,000	230,000
FHLBB and correspondent bank overnight borrowings	43,100	38,800
Capital lease obligation	63	60
Notes payable	0	25
Long-term Debt [Member]
Debt Instrument [Line Items]
Securities Sold under Agreements to Repurchase	30,097	30,142
Capital lease obligation	$ 921	$ 984

FHLBB and Correspondent Bank Overnight Borrowings

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Amount of capital lease obligation due within one year or the normal operating cycle, if longer.

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Amount equal to the present value (the principal) at the beginning of the lease term of minimum lease payments during the lease term (excluding that portion of the payments representing executory costs such as insurance, maintenance, and taxes to be paid by the lessor, together with any profit thereon) net of payments or other amounts applied to the principal, through the balance sheet date and due to be paid more than one year (or one operating cycle, if longer) after the balance sheet date.

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Sum of the carrying values as of the balance sheet date of all debt, including all short-term borrowings, long-term debt, and capital lease obligations.

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Amount of advances from Federal Home Loan Bank (FHLBank) maturing in the next fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Carrying amount of long-term debt, net of unamortized discount or premium, including current and noncurrent amounts. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Sum of the carrying values as of the balance sheet date of the portions of long-term notes payable due within one year or the operating cycle if longer.

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Amount, after the effects of master netting arrangements, of funds outstanding borrowed in the form of a security repurchase agreement between the entity and another party for the sale and repurchase of identical or substantially the same securities at a date certain for a specified price. Includes liabilities not subject to a master netting arrangement and not elected to be offset.

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Reflects the total carrying amount as of the balance sheet date of debt having initial terms less than one year or the normal operating cycle, if longer.

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