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, 2013	Dec. 31, 2012
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 40,554	$ 35,737
Accumulated Amortization	18,498	17,251
Net Carrying Amount	22,056	18,486
Core Deposits [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	11,668	11,668
Accumulated Amortization	9,702	9,327
Net Carrying Amount	1,966	2,341
Mortgage Servicing Rights [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	27,709	22,892
Accumulated Amortization	8,088	7,239
Net Carrying Amount	19,621	15,653
Customer Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	1,177	1,177
Accumulated Amortization	708	685
Net Carrying Amount	$ 469	$ 492