Goodwill and Other Intangible Assets - Other Intangible Assets (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Gross Intangible Assets	$ 171,769	$ 126,621
Accumulated Amortization	(94,696)	(83,643)
Valuation Allowance	(83)	(471)
Net Intangible Assets	76,990	42,507
Loan servicing rights
Finite-Lived Intangible Assets [Line Items]
Gross Intangible Assets	87,354	79,138
Accumulated Amortization	(63,161)	(57,054)
Valuation Allowance	(83)	(471)
Net Intangible Assets	24,110	21,613
Core deposits
Finite-Lived Intangible Assets [Line Items]
Gross Intangible Assets	80,470	43,396
Accumulated Amortization	(29,136)	(24,297)
Valuation Allowance	0	0
Net Intangible Assets	51,334	19,099
Other
Finite-Lived Intangible Assets [Line Items]
Gross Intangible Assets	3,945	4,087
Accumulated Amortization	(2,399)	(2,292)
Valuation Allowance	0	0
Net Intangible Assets	$ 1,546	$ 1,795