Goodwill and Other Intangible Assets - Other Intangible Assets (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Finite-Lived Intangible Assets [Line Items]
Gross Intangible Assets	$ 104,449	$ 85,311
Accumulated Amortization	(70,280)	(61,823)
Valuation Allowance	(3,046)	(2,670)
Net Intangible Assets	31,123	20,818
Loan servicing rights [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Intangible Assets	63,377	52,046
Accumulated Amortization	(43,393)	(39,146)
Valuation Allowance	(3,046)	(2,670)
Net Intangible Assets	16,938	10,230
Core deposits [member]
Finite-Lived Intangible Assets [Line Items]
Gross Intangible Assets	35,194	27,144
Accumulated Amortization	(24,160)	(20,363)
Valuation Allowance
Net Intangible Assets	11,034	6,781
Other [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Intangible Assets	5,878	6,121
Accumulated Amortization	(2,727)	(2,314)
Valuation Allowance
Net Intangible Assets	$ 3,151	$ 3,807