Borrowings (Schedule of Other Borrowed Funds) (Details) - USD ($) $ in Thousands		Dec. 31, 2016	Dec. 31, 2015
Debt Instrument [Line Items]
Securities Sold under Agreements to Repurchase	[1]	$ 230,612	$ 215,041
Total short-term borrowings		530,129	477,852
Total long-term borrowings		10,791	35,911
Short-term Debt [Member]
Debt Instrument [Line Items]
Securities Sold under Agreements to Repurchase		225,605	184,989
FHLBB borrowings		210,000	255,000
FHLBB and correspondent bank overnight borrowings		89,450	12,800
Capital lease obligation		67	63
Long-term Debt [Member]
Debt Instrument [Line Items]
Securities Sold under Agreements to Repurchase		0	5,052
Long-term Federal Home Loan Bank Advances		10,000	30,000
Capital lease obligation		791	859
Commercial and Industrial Sector [Member] | Short-term Debt [Member]
Debt Instrument [Line Items]
Securities Sold under Agreements to Repurchase		$ 5,007	$ 25,000

[1] (1) Total repurchase agreements are presented within short-term borrowings on the consolidated statements of condition.