Goodwill, Core Deposit Premium and Other Intangible Assets (Carrying amount of intangible assets (incl accumulated amortization) (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 111,807	$ 101,652
Accumulated Amortization	48,180	43,099
Net Carrying Amount	63,627	58,553
Core deposit intangibles
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	62,008	43,504
Accumulated Amortization	25,271	21,049
Net Carrying Amount	36,737	22,455
Customer relationship intangibles
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	1,177	1,177
Accumulated Amortization	886	857
Net Carrying Amount	291	320
Mortgage servicing rights
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	41,903	50,467
Accumulated Amortization	18,161	18,379
Net Carrying Amount	23,742	32,088
Commercial servicing rights
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	6,719	6,504
Accumulated Amortization	3,862	2,814
Net Carrying Amount	$ 2,857	$ 3,690