Investment Securities (Available-for-sale Securities with Unrealized Loss) (Details) (USD $)	Sep. 30, 2013 securities	Dec. 31, 2012 securities
Available-for-sale securities that had an unrealized loss:
Less than 12 months, unrealized loss	$ 14,049,000	$ 2,469,000
Less than 12 months, no. of securities	114	40
12 months or more, fair value	47,572,000	95,483,000
12 months or more, unrealized loss	4,196,000	8,190,000
12 months or more, no. of securities	19	26
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	428,625,000	245,348,000
Total unrealized loss	18,245,000	10,659,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	381,053,000	149,865,000
U.S. Treasury and government agencies
Available-for-sale securities that had an unrealized loss:
Less than 12 months, unrealized loss	0	0
Less than 12 months, no. of securities	0	0
12 months or more, fair value	0	0
12 months or more, unrealized loss	0	0
12 months or more, no. of securities	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	0	0
Total unrealized loss	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	0	0
U.S. government sponsored agencies
Available-for-sale securities that had an unrealized loss:
Less than 12 months, unrealized loss	0	0
Less than 12 months, no. of securities	0	0
12 months or more, fair value	0	0
12 months or more, unrealized loss	0	0
12 months or more, no. of securities	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	0	0
Total unrealized loss	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	0	0
States and political subdivisions
Available-for-sale securities that had an unrealized loss:
Less than 12 months, unrealized loss	1,134,000	82,000
Less than 12 months, no. of securities	30	8
12 months or more, fair value	0	0
12 months or more, unrealized loss	0	0
12 months or more, no. of securities	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	21,026,000	4,558,000
Total unrealized loss	1,134,000	82,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	21,026,000	4,558,000
Residential mortgage-backed securities
Available-for-sale securities that had an unrealized loss:
Less than 12 months, unrealized loss	12,090,000	2,326,000
Less than 12 months, no. of securities	77	28
12 months or more, fair value	37,716,000	89,958,000
12 months or more, unrealized loss	3,333,000	7,441,000
12 months or more, no. of securities	12	20
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	372,078,000	225,208,000
Total unrealized loss	15,423,000	9,767,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	334,362,000	135,250,000
Commercial mortgage-backed securities
Available-for-sale securities that had an unrealized loss:
Less than 12 months, unrealized loss	750,000	43,000
Less than 12 months, no. of securities	5	2
12 months or more, fair value	4,933,000	0
12 months or more, unrealized loss	217,000	0
12 months or more, no. of securities	1	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	27,561,000	7,681,000
Total unrealized loss	967,000	43,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	22,628,000	7,681,000
Bank-issued trust preferred securities
Available-for-sale securities that had an unrealized loss:
Less than 12 months, unrealized loss	75,000	18,000
Less than 12 months, no. of securities	2	2
12 months or more, fair value	4,831,000	5,434,000
12 months or more, unrealized loss	560,000	664,000
12 months or more, no. of securities	4	5
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	7,868,000	7,810,000
Total unrealized loss	635,000	682,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	3,037,000	2,376,000
Number of available-for-sale securities in unrealized loss position for twelve months or more	4
Available-for-sale securities in unrealized loss position, aggregate book value	5,400,000
Equity Securities
Available-for-sale securities that had an unrealized loss:
Less than 12 months, unrealized loss	0	0
Less than 12 months, no. of securities	0	0
12 months or more, fair value	92,000	91,000
12 months or more, unrealized loss	86,000	85,000
12 months or more, no. of securities	2	1
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	92,000	91,000
Total unrealized loss	86,000	85,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	0	0
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Available-for-sale securities that had an unrealized loss:
Percentage of mortgage-backed securities in unrealized loss position for more than 12 months	93.00%
Mortgage-backed Securities, Issued by Private Enterprises [Member]
Available-for-sale securities that had an unrealized loss:
Less than 12 months, no. of securities	5
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, More than 12 Months, Number of Positions with Fair Value Less than 90% of Book Value	2
Percentage of mortgage-backed securities in unrealized loss position for more than 12 months	7.00%
Fair value within book value	90.00%
Fair Value Less Than 90 Percent of Book Value [Member] | Mortgage-backed Securities, Issued by Private Enterprises [Member]
Available-for-sale securities that had an unrealized loss:
12 months or more, fair value	800,000
Mortgage-backed securities in unrealized loss position for more than 12 months, aggregate book value	$ 900,000