Loans and the Allowance for Loan Losses (Details 9) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Fair value of loans determined to be impaired and not to be impaired at the time of acquisition
Loans acquired with deteriorated credit quality	$ 271,663	$ 348,626
Contractually-required principal and interest [Member]
Fair value of loans determined to be impaired and not to be impaired at the time of acquisition
Loans acquired with deteriorated credit quality	326,014
Nonaccretable difference [Member]
Fair value of loans determined to be impaired and not to be impaired at the time of acquisition
Loans acquired with deteriorated credit quality	(45,216)
Cash flows expected to be collected [Member]
Fair value of loans determined to be impaired and not to be impaired at the time of acquisition
Loans acquired with deteriorated credit quality	280,798
Accretable yield [Member]
Fair value of loans determined to be impaired and not to be impaired at the time of acquisition
Loans acquired with deteriorated credit quality	(9,135)
Impaired Covered Loans [Member]
Fair value of loans determined to be impaired and not to be impaired at the time of acquisition
Loans acquired with deteriorated credit quality	42,633	61,315
Impaired Covered Loans [Member] | Contractually-required principal and interest [Member]
Fair value of loans determined to be impaired and not to be impaired at the time of acquisition
Loans acquired with deteriorated credit quality	62,369
Impaired Covered Loans [Member] | Nonaccretable difference [Member]
Fair value of loans determined to be impaired and not to be impaired at the time of acquisition
Loans acquired with deteriorated credit quality	(19,720)
Impaired Covered Loans [Member] | Cash flows expected to be collected [Member]
Fair value of loans determined to be impaired and not to be impaired at the time of acquisition
Loans acquired with deteriorated credit quality	42,649
Impaired Covered Loans [Member] | Accretable yield [Member]
Fair value of loans determined to be impaired and not to be impaired at the time of acquisition
Loans acquired with deteriorated credit quality	(16)
Other Covered Loans [Member]
Fair value of loans determined to be impaired and not to be impaired at the time of acquisition
Loans acquired with deteriorated credit quality	217,912	278,147
Other Covered Loans [Member] | Contractually-required principal and interest [Member]
Fair value of loans determined to be impaired and not to be impaired at the time of acquisition
Loans acquired with deteriorated credit quality	250,161
Other Covered Loans [Member] | Nonaccretable difference [Member]
Fair value of loans determined to be impaired and not to be impaired at the time of acquisition
Loans acquired with deteriorated credit quality	(24,298)
Other Covered Loans [Member] | Cash flows expected to be collected [Member]
Fair value of loans determined to be impaired and not to be impaired at the time of acquisition
Loans acquired with deteriorated credit quality	225,863
Other Covered Loans [Member] | Accretable yield [Member]
Fair value of loans determined to be impaired and not to be impaired at the time of acquisition
Loans acquired with deteriorated credit quality	(7,951)
Not Covered Loans [Member]
Fair value of loans determined to be impaired and not to be impaired at the time of acquisition
Loans acquired with deteriorated credit quality	11,118	9,164
Not Covered Loans [Member] | Contractually-required principal and interest [Member]
Fair value of loans determined to be impaired and not to be impaired at the time of acquisition
Loans acquired with deteriorated credit quality	13,484
Not Covered Loans [Member] | Nonaccretable difference [Member]
Fair value of loans determined to be impaired and not to be impaired at the time of acquisition
Loans acquired with deteriorated credit quality	(1,198)
Not Covered Loans [Member] | Cash flows expected to be collected [Member]
Fair value of loans determined to be impaired and not to be impaired at the time of acquisition
Loans acquired with deteriorated credit quality	12,286
Not Covered Loans [Member] | Accretable yield [Member]
Fair value of loans determined to be impaired and not to be impaired at the time of acquisition
Loans acquired with deteriorated credit quality	$ (1,168)