Goodwill, Core Deposit Premium and Other Intangible Assets (Carrying amount of intangible assets (incl accumulated amortization) (Details) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 74,140	$ 60,071
Accumulated Amortization	28,914	26,139
Net Carrying Amount	45,226	33,932
Core deposit intangibles
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	27,109	21,069
Accumulated Amortization	13,849	12,525
Net Carrying Amount	13,260	8,544
Mortgage servicing rights
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	41,458	37,825
Accumulated Amortization	13,819	12,841
Net Carrying Amount	27,639	24,984
Customer relationship intangible
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	1,177	1,177
Accumulated Amortization	794	773
Net Carrying Amount	383	404
Commercial servicing rights
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	4,396	0
Accumulated Amortization	452	0
Net Carrying Amount	$ 3,944	$ 0