Goodwill, Core Deposit Premium and Other Intangible Assets (Estimated future amortization expense for amortizable intangible assets) (Details) $ in Thousands	Sep. 30, 2017 USD ($)
Future amortization expense for amortizable intangible assets [Line Items]
Three months ending December 31, 2017	$ 4,472
Year ending December 31,
2018	12,771
2019	11,079
2020	9,470
2021	7,880
2022	6,012
Thereafter	11,943
Total	63,627
Core deposit intangibles
Future amortization expense for amortizable intangible assets [Line Items]
Three months ending December 31, 2017	1,815
Year ending December 31,
2018	6,712
2019	5,915
2020	5,191
2021	4,425
2022	3,391
Thereafter	9,288
Total	36,737
Customer relationship intangibles
Future amortization expense for amortizable intangible assets [Line Items]
Three months ending December 31, 2017	10
Year ending December 31,
2018	39
2019	38
2020	37
2021	35
2022	34
Thereafter	98
Total	291
Mortgage servicing rights
Future amortization expense for amortizable intangible assets [Line Items]
Three months ending December 31, 2017	2,463
Year ending December 31,
2018	5,319
2019	4,560
2020	3,800
2021	3,040
2022	2,280
Thereafter	2,280
Total	23,742
Commercial servicing rights
Future amortization expense for amortizable intangible assets [Line Items]
Three months ending December 31, 2017	184
Year ending December 31,
2018	701
2019	566
2020	442
2021	380
2022	307
Thereafter	277
Total	$ 2,857