Other Intangible Assets (Detail) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2012	Dec. 31, 2011
Finite-Lived Intangible Assets [Line Items]
Gross Intangible Assets	$ 99,984	$ 85,311
Accumulated Amortization	(68,060)	(61,823)
Valuation Allowance	(3,052)	(2,670)
Net Intangible Assets	28,872	20,818
Loan servicing rights
Finite-Lived Intangible Assets [Line Items]
Gross Intangible Assets	58,912	52,046
Accumulated Amortization	(42,233)	(39,146)
Valuation Allowance	(3,052)	(2,670)
Net Intangible Assets	13,627	10,230
Core deposits
Finite-Lived Intangible Assets [Line Items]
Gross Intangible Assets	35,194	27,144
Accumulated Amortization	(23,263)	(20,363)
Net Intangible Assets	11,931	6,781
Other
Finite-Lived Intangible Assets [Line Items]
Gross Intangible Assets	5,878	6,121
Accumulated Amortization	(2,564)	(2,314)
Net Intangible Assets	$ 3,314	$ 3,807