Goodwill and Other Intangible Assets - Estimated Future Amortization Expense (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012
Loan servicing rights [Member]
Finite-Lived Intangible Assets [Line Items]
2013	$ 4,511
2014	3,640
2015	2,658
2016	1,941
2017	1,433
Core deposits [member]
Finite-Lived Intangible Assets [Line Items]
2013	3,078
2014	2,359
2015	1,758
2016	1,195
2017	815
Other [Member]
Finite-Lived Intangible Assets [Line Items]
2013	541
2014	466
2015	434
2016	233
2017	$ 220

Amount of amortization expense expected to be recognized during the next fiscal year following the latest fiscal year for assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 30

-Section 50

-Paragraph 2

-Subparagraph (a)(3)

-URI http://asc.fasb.org/extlink&oid=7658586&loc=d3e16323-109275

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Amount of amortization expense expected to be recognized during the fifth fiscal year following the latest fiscal year for assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

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Amount of amortization expense expected to be recognized during the fourth fiscal year following the latest fiscal year for assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

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Amount of amortization expense expected to be recognized during the third fiscal year following the latest fiscal year for assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

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Amount of amortization expense expected to be recognized during the second fiscal year following the latest fiscal year for assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

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