Goodwill and Other Intangible Assets - Schedule of Change in Loan Servicing Rights (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Goodwill [Roll Forward]
Balance at beginning of year	$ 26,068us-gaap_ServicingAssetAtAmortizedValue	$ 19,984us-gaap_ServicingAssetAtAmortizedValue	$ 12,900us-gaap_ServicingAssetAtAmortizedValue
Origination of loan servicing rights	1,065	13,265	12,039
Amortization expense	(6,687)	(7,181)	(4,955)
Balance at end of year	20,446us-gaap_ServicingAssetAtAmortizedValue	26,068us-gaap_ServicingAssetAtAmortizedValue	19,984us-gaap_ServicingAssetAtAmortizedValue
Balance at beginning of year	(504)	(3,046)	(2,670)
Impairment adjustment	(88)	2,542	(376)
Balance at end of year	(592)	(504)	(3,046)
Balance at end of year, net of valuation allowance	$ 19,854	$ 25,564	$ 16,938

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Amortized amount of contract to service financial assets under which the benefits of servicing are expected to more than adequately compensate the servicer.

+ References

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-Publisher FASB

-Name Accounting Standards Codification

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Amount of additions from purchases, assumption or transfer to contract to service financial assets under which the benefits of servicing are expected to more than adequately compensate the servicer.

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Amount of amortization of contract to service financial assets under which the benefits of servicing are expected to more than adequately compensate the servicer.

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Fair value of contract to service financial assets under which the benefits of servicing are expected to more than adequately compensate the servicer.

+ References

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Reflects the estimated amount of impairment as of the balance sheet date of recognized servicing assets that are being amortized in proportion to and over the period of estimated net servicing income or loss.

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The net increase (decrease) in the valuation allowance for servicing assets subsequently measured using the amortization method.

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