Goodwill and Other Intangible Assets - Other Intangible Assets (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Jan. 01, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Gross Intangible Assets	$ 169,371		$ 126,621
Accumulated Amortization	(85,251)		(83,643)
Valuation Allowance	(154)		(471)
Net Intangible Assets	83,966		42,507
Loan servicing rights
Finite-Lived Intangible Assets [Line Items]
Gross Intangible Assets	84,956	$ 1,400	79,138
Accumulated Amortization	(59,975)		(57,054)
Valuation Allowance	(154)		(471)
Net Intangible Assets	24,827		21,613
Core deposits
Finite-Lived Intangible Assets [Line Items]
Gross Intangible Assets	80,470	$ 44,600	43,396
Accumulated Amortization	(23,002)		(24,297)
Valuation Allowance	0		0
Net Intangible Assets	57,468		19,099
Other
Finite-Lived Intangible Assets [Line Items]
Gross Intangible Assets	3,945		4,087
Accumulated Amortization	(2,274)		(2,292)
Valuation Allowance	0		0
Net Intangible Assets	$ 1,671		$ 1,795