Goodwill, Core Deposit Premium and Other Intangible Assets (Carrying amount of intangible assets (incl accumulated amortization) (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 99,316	$ 89,724
Accumulated Amortization	38,449	32,779
Net Carrying Amount	60,867	56,945
Core deposit intangibles
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	43,504	37,118
Accumulated Amortization	18,632	15,460
Net Carrying Amount	24,872	21,658
Mortgage servicing rights
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	48,355	45,744
Accumulated Amortization	17,068	15,430
Net Carrying Amount	31,287	30,314
Customer relationship intangible
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	1,177	1,177
Accumulated Amortization	836	815
Net Carrying Amount	341	362
Commercial servicing rights
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	6,280	5,685
Accumulated Amortization	1,913	1,074
Net Carrying Amount	$ 4,367	$ 4,611