Investment Securities (Available-for-sale Securities with Unrealized Loss) (Details) (USD $)	Jun. 30, 2013 securities	Dec. 31, 2012 securities
Available-for-sale securities that had an unrealized loss:
Less than 12 months, fair value	$ 364,553,000	$ 149,865,000
Less than 12 months, unrealized loss	14,515,000	2,469,000
Less than 12 months, no. of securities	108	40
12 months or more, fair value	30,559,000	95,483,000
12 months or more, unrealized loss	3,346,000	8,190,000
12 months or more, no. of securities	14	26
Total fair value	395,112,000	245,348,000
Total unrealized loss	17,861,000	10,659,000
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 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 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	20,244,000	4,558,000
Less than 12 months, unrealized loss	1,044,000	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
Total fair value	20,244,000	4,558,000
Total unrealized loss	1,044,000	82,000
Residential mortgage-backed securities
Available-for-sale securities that had an unrealized loss:
Less than 12 months, fair value	316,939,000	135,250,000
Less than 12 months, unrealized loss	12,779,000	2,326,000
Less than 12 months, no. of securities	71	28
12 months or more, fair value	22,945,000	89,958,000
12 months or more, unrealized loss	2,620,000	7,441,000
12 months or more, no. of securities	9	20
Total fair value	339,884,000	225,208,000
Total unrealized loss	15,399,000	9,767,000
Commercial mortgage-backed securities
Available-for-sale securities that had an unrealized loss:
Less than 12 months, fair value	22,996,000	7,681,000
Less than 12 months, unrealized loss	579,000	43,000
Less than 12 months, no. of securities	5	2
12 months or more, fair value	5,103,000	0
12 months or more, unrealized loss	64,000	0
12 months or more, no. of securities	1	0
Total fair value	28,099,000	7,681,000
Total unrealized loss	643,000	43,000
Bank-issued trust preferred securities
Available-for-sale securities that had an unrealized loss:
Less than 12 months, fair value	4,374,000	2,376,000
Less than 12 months, unrealized loss	113,000	18,000
Less than 12 months, no. of securities	2	2
12 months or more, fair value	2,421,000	5,434,000
12 months or more, unrealized loss	576,000	664,000
12 months or more, no. of securities	3	5
Total fair value	6,795,000	7,810,000
Total unrealized loss	689,000	682,000
Number of available-for-sale securities in unrealized loss position	3
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	91,000
12 months or more, unrealized loss	86,000	85,000
12 months or more, no. of securities	1	1
Total fair value	90,000	91,000
Total unrealized loss	86,000	85,000
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 less than 12 months	89.00%
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
Percentage of mortgage-backed securities in unrealized loss position for less than 12 months	11.00%
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:
Less than 12 months, fair value	1,700,000
Mortgage-backed securities in unrealized loss position for less than 12 months, aggregate book value	1,900,000
Fair Value Less Than 95 Percent of Book Value [Member] | Bank-issued trust preferred securities
Available-for-sale securities that had an unrealized loss:
Total fair value	2,400,000
Available-for-sale securities in unrealized loss position, aggregate book value	$ 3,000,000
Fair Value Within 95 Percent of Book Value [Member] | Bank-issued trust preferred securities
Available-for-sale securities that had an unrealized loss:
Number of available-for-sale securities in unrealized loss position	3