Investment Securities Gross Unrealized Losses and Fair Values of Investment Securities (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012 securities	Dec. 31, 2011 securities
Available-for-Sale:
Available-for-Sale, Less Than 12 Months Fair Value	$ 155,991	$ 333,344
Available-for-Sale, Less Than 12 Months Gross Unrealized Losses	(1,305)	(686)
Available-for-Sale, 12 Months or More Fair Value	154	177
Available-for-Sale, 12 Months or More Gross Unrealized Losses	(1)	(6)
Available-for-Sale, Total Fair Value	156,145	333,521
Available-for-Sale, Total Gross Unrealized Losses	(1,306)	(692)
Available-for-Sale and Held-to-Maturity:
Investment Securities in an Unrealized Loss Position (Number of Securities)	30	24
Obligations of U.S. government agencies
Available-for-Sale:
Available-for-Sale, Less Than 12 Months Fair Value	31,855	287,404
Available-for-Sale, Less Than 12 Months Gross Unrealized Losses	(39)	(662)
Available-for-Sale, 12 Months or More Fair Value	0	0
Available-for-Sale, 12 Months or More Gross Unrealized Losses	0	0
Available-for-Sale, Total Fair Value	31,855	287,404
Available-for-Sale, Total Gross Unrealized Losses	(39)	(662)
U.S. agency residential mortgage-backed securities & collateralized mortgage obligations
Available-for-Sale:
Available-for-Sale, Less Than 12 Months Fair Value	124,136	45,694
Available-for-Sale, Less Than 12 Months Gross Unrealized Losses	(1,266)	(14)
Available-for-Sale, 12 Months or More Fair Value	0	0
Available-for-Sale, 12 Months or More Gross Unrealized Losses	0	0
Available-for-Sale, Total Fair Value	124,136	45,694
Available-for-Sale, Total Gross Unrealized Losses	(1,266)	(14)
Private mortgage-backed securities
Available-for-Sale:
Available-for-Sale, Less Than 12 Months Fair Value	0	246
Available-for-Sale, Less Than 12 Months Gross Unrealized Losses	0	(10)
Available-for-Sale, 12 Months or More Fair Value	154	177
Available-for-Sale, 12 Months or More Gross Unrealized Losses	(1)	(6)
Available-for-Sale, Total Fair Value	154	423
Available-for-Sale, Total Gross Unrealized Losses	(1)	(16)
State, county and municipal securities
Held-to-Maturity:
Held-to-Maturity, Less than 12 Months Fair Value	4,961	0
Held-to-Maturity, Less than 12 Months Gross Unrealized Losses	(39)	0
Held-to-Maturity, 12 Months or More Fair Value	696	773
Held-to-Maturity, 12 Months or More Gross Unrealized Losses	(8)	(17)
Held-to-Maturity, Total Fair Value	5,657	773
Held-to-Maturity, Total Gross Unrealized Losses	$ (47)	$ (17)

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