Goodwill and Other Intangible Assets - Other Intangible Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Jan. 01, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Gross Intangible Assets	$ 170,813		$ 126,621
Accumulated Amortization	(89,936)		(83,643)
Valuation Allowance	(106)		(471)
Net Intangible Assets	80,771		42,507
Loan servicing rights
Finite-Lived Intangible Assets [Line Items]
Gross Intangible Assets	86,398	$ 1,400	79,138
Accumulated Amortization	(61,507)		(57,054)
Valuation Allowance	(106)		(471)
Net Intangible Assets	24,785		21,613
Core deposits
Finite-Lived Intangible Assets [Line Items]
Gross Intangible Assets	80,470	$ 44,600	43,396
Accumulated Amortization	(26,092)		(24,297)
Valuation Allowance	0		0
Net Intangible Assets	54,378		19,099
Other
Finite-Lived Intangible Assets [Line Items]
Gross Intangible Assets	3,945		4,087
Accumulated Amortization	(2,337)		(2,292)
Valuation Allowance	0		0
Net Intangible Assets	$ 1,608		$ 1,795