Goodwill, Core Deposit Premium and Other Intangible Assets (Estimated future amortization expense for amortizable intangible assets) (Details) $ in Thousands	Mar. 31, 2016 USD ($)
Future amortization expense for amortizable intangible assets [Line Items]
Nine months ending December 31, 2016	$ 11,245
Year ending December 31,
2017	11,308
2018	9,858
2019	8,329
2020	6,855
2021	5,426
Thereafter	8,399
Total	61,420
Core deposit intangibles
Future amortization expense for amortizable intangible assets [Line Items]
Nine months ending December 31, 2016	3,716
Year ending December 31,
2017	4,419
2018	3,909
2019	3,426
2020	2,982
2021	2,463
Thereafter	5,244
Total	26,159
Mortgage servicing rights
Future amortization expense for amortizable intangible assets [Line Items]
Nine months ending December 31, 2016	6,778
Year ending December 31,
2017	5,918
2018	5,073
2019	4,227
2020	3,382
2021	2,536
Thereafter	2,536
Total	30,450
Customer relationship intangible
Future amortization expense for amortizable intangible assets [Line Items]
Nine months ending December 31, 2016	31
Year ending December 31,
2017	40
2018	39
2019	38
2020	36
2021	35
Thereafter	132
Total	351
Commercial servicing rights
Future amortization expense for amortizable intangible assets [Line Items]
Nine months ending December 31, 2016	720
Year ending December 31,
2017	931
2018	837
2019	638
2020	455
2021	392
Thereafter	487
Total	$ 4,460