Goodwill, Core Deposit Premium and Other Intangible Assets (Estimated future amortization expense for amortizable intangible assets) (Details) $ in Thousands	Sep. 30, 2015 USD ($)
Future amortization expense for amortizable intangible assets [Line Items]
Three months ending December 31, 2015	$ 3,074
Year ending December 31,
2016	10,557
2017	9,208
2018	7,852
2019	6,417
2020	4,968
Thereafter	6,619
Total	48,695
Core deposit intangibles
Future amortization expense for amortizable intangible assets [Line Items]
Three months ending December 31, 2015	755
Year ending December 31,
2016	2,772
2017	2,452
2018	2,169
2019	1,886
2020	1,619
Thereafter	2,913
Total	14,566
Mortgage servicing rights
Future amortization expense for amortizable intangible assets [Line Items]
Three months ending December 31, 2015	2,087
Year ending December 31,
2016	6,878
2017	5,896
2018	4,913
2019	3,930
2020	2,948
Thereafter	2,948
Total	29,600
Customer relationship intangible
Future amortization expense for amortizable intangible assets [Line Items]
Three months ending December 31, 2015	11
Year ending December 31,
2016	41
2017	40
2018	39
2019	38
2020	37
Thereafter	166
Total	372
Commercial servicing rights
Future amortization expense for amortizable intangible assets [Line Items]
Three months ending December 31, 2015	221
Year ending December 31,
2016	866
2017	820
2018	731
2019	563
2020	364
Thereafter	592
Total	$ 4,157