Investment Securities (Narrative) (Details) (USD $)	3 Months Ended		9 Months Ended			3 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012	Sep. 30, 2013 Transferred From Available-For-Sale to Held-To-Maturity [Member]	Sep. 30, 2013 Unrealized (Gains) Losses on Securities [Member] Transferred From Available-For-Sale to Held-To-Maturity [Member]	Jun. 30, 2013 Unrealized (Gains) Losses on Securities [Member] Transferred From Available-For-Sale to Held-To-Maturity [Member]	Mar. 31, 2013 Unrealized (Gains) Losses on Securities [Member] Transferred From Available-For-Sale to Held-To-Maturity [Member]
Schedule of Available-for-sale Securities [Line Items]
Book value of securities pledged	$ 264,350,000		$ 264,350,000		$ 349,520,000
Securities held to maturity, fair value	134,118,000		134,118,000		454,000
Securities transferred from available-for-sale to held-to-maturity category, amortized cost			144,428,000	0		144,430,000
Securities transferred from available-for-sale to held-to-maturity category, fair value						139,570,000
Securities transferred from available-for-sale to held-to-maturity category, unrealized holding loss	3,159,000	0	3,159,000	0			3,159,000
Securities transferred from available-for-sale to held-to-maturity category, remaining unamortized loss	(2,698,000)	(1,047,000)	5,440,000	(1,266,000)			3,030,000	0	0
Investment in FHLBB stock	7,496,000		7,496,000		8,145,000
Dividend income on investment in federal home loan bank stock	$ 7,000	$ 11,000	$ 20,000	$ 36,000