Goodwill and Other Intangible Assets - Other Intangible Assets (Detail) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2015	Dec. 31, 2014
Finite-Lived Intangible Assets [Line Items]
Gross Intangible Assets	$ 123,235	$ 123,439
Accumulated Amortization	(91,470)	(84,072)
Valuation Allowance	(383)	(592)
Net Intangible Assets	31,382	38,775
Loan Servicing Rights
Finite-Lived Intangible Assets [Line Items]
Gross Intangible Assets	75,477	72,154
Accumulated Amortization	(58,027)	(51,708)
Valuation Allowance	(383)	(592)
Net Intangible Assets	17,067	19,854
Core Deposits
Finite-Lived Intangible Assets [Line Items]
Gross Intangible Assets	43,384	46,694
Accumulated Amortization	(30,888)	(29,916)
Valuation Allowance	0	0
Net Intangible Assets	12,496	16,778
Other
Finite-Lived Intangible Assets [Line Items]
Gross Intangible Assets	4,374	4,591
Accumulated Amortization	(2,555)	(2,448)
Valuation Allowance	0	0
Net Intangible Assets	$ 1,819	$ 2,143