Investment Securities (Available-for-sale Securities with Unrealized Loss) (Details) (USD $)	Mar. 31, 2014 securities	Dec. 31, 2013 securities
Available-for-sale securities that had an unrealized loss:
Less than 12 months, fair value	$ 313,649,000	$ 347,736,000
Less than 12 months, unrealized loss	10,354,000	18,237,000
Less than 12 months, no. of securities	83	102
12 months or more, fair value	99,924,000	75,725,000
12 months or more, unrealized loss	6,639,000	7,301,000
12 months or more, no. of securities	42	38
Total unrealized loss position, fair value	413,573,000	423,461,000
Total unrealized loss	16,993,000	25,538,000
U.S. Treasury and government agencies
Available-for-sale securities that had an unrealized loss:
Less than 12 months, fair value	0	0
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
Total unrealized loss position, fair value	0	0
Total unrealized loss	0	0
U.S. government sponsored agencies
Available-for-sale securities that had an unrealized loss:
Less than 12 months, fair value	0	0
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
Total unrealized loss position, fair value	0	0
Total unrealized loss	0	0
States and political subdivisions
Available-for-sale securities that had an unrealized loss:
Less than 12 months, fair value	12,445,000	15,848,000
Less than 12 months, unrealized loss	251,000	659,000
Less than 12 months, no. of securities	18	22
12 months or more, fair value	5,440,000	6,180,000
12 months or more, unrealized loss	260,000	368,000
12 months or more, no. of securities	9	10
Total unrealized loss position, fair value	17,885,000	22,028,000
Total unrealized loss	511,000	1,027,000
Residential mortgage-backed securities
Available-for-sale securities that had an unrealized loss:
Less than 12 months, fair value	279,545,000	310,315,000
Less than 12 months, unrealized loss	9,400,000	16,709,000
Less than 12 months, no. of securities	60	75
12 months or more, fair value	83,715,000	57,440,000
12 months or more, unrealized loss	5,342,000	5,811,000
12 months or more, no. of securities	26	20
Total unrealized loss position, fair value	363,260,000	367,755,000
Total unrealized loss	14,742,000	22,520,000
Commercial mortgage-backed securities
Available-for-sale securities that had an unrealized loss:
Less than 12 months, fair value	19,556,000	19,560,000
Less than 12 months, unrealized loss	696,000	779,000
Less than 12 months, no. of securities	4	4
12 months or more, fair value	7,194,000	7,205,000
12 months or more, unrealized loss	439,000	447,000
12 months or more, no. of securities	2	2
Total unrealized loss position, fair value	26,750,000	26,765,000
Total unrealized loss	1,135,000	1,226,000
Bank-issued trust preferred securities
Available-for-sale securities that had an unrealized loss:
Less than 12 months, fair value	2,103,000	2,013,000
Less than 12 months, unrealized loss	7,000	90,000
Less than 12 months, no. of securities	1	1
12 months or more, fair value	3,485,000	4,803,000
12 months or more, unrealized loss	513,000	589,000
12 months or more, no. of securities	4	4
Total unrealized loss position, fair value	5,588,000	6,816,000
Total unrealized loss	520,000	679,000
Number of bank-issued trust preferred securities in unrealized loss position for twelve months or more	4
Equity securities
Available-for-sale securities that had an unrealized loss:
Less than 12 months, fair value	0	0
Less than 12 months, unrealized loss	0	0
Less than 12 months, no. of securities	0	0
12 months or more, fair value	90,000	97,000
12 months or more, unrealized loss	85,000	86,000
12 months or more, no. of securities	1	2
Total unrealized loss position, fair value	90,000	97,000
Total unrealized loss	85,000	86,000
Mortgage-backed securities, issued by US government sponsored agencies
Available-for-sale securities that had an unrealized loss:
Percentage of mortgage-backed securities in unrealized loss position for more than 12 months	98.00%
Mortgage-backed securities, privately issued
Available-for-sale securities that had an unrealized loss:
Less than 12 months, no. of securities	4
Number of privately issued mortgage-backed securities securities with book value less than 90% of fair value	2
Percentage of mortgage-backed securities in unrealized loss position for more than 12 months	2.00%
Fair value within book value	90.00%
Fair Value Less Than 90 Percent of Book Value [Member] | Mortgage-backed securities, privately issued
Available-for-sale securities that had an unrealized loss:
12 months or more, fair value	600,000
Book value of privately issued mortgage-backed securities in unrealized loss position for more than 12 months	$ 900,000