Goodwill, Core Deposit Premium and Other Intangible Assets Carrying amount of intangible assets (incl accumulated amortization) (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 30,248	$ 27,913
Accumulated Amortization	15,953	14,953
Net Carrying Amount	14,295	12,960
Core Deposits [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	9,957	9,957
Accumulated Amortization	9,034	8,815
Net Carrying Amount	923	1,142
Servicing Contracts [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	19,114	16,779
Accumulated Amortization	6,250	5,503
Net Carrying Amount	12,864	11,276
Customer Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	1,177	1,177
Accumulated Amortization	669	635
Net Carrying Amount	$ 508	$ 542