Derivative Financial Instruments - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013
Derivative [Line Items]
Forward sales of mortgage-backed securities	$ 64.5
Interest Rate Lock Commitments [Member]
Derivative [Line Items]
Derivative financial instruments	$ 73.6

Fair value of the assets less the liabilities of a derivative or group of derivatives.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

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Reference 2: http://www.xbrl.org/2003/role/presentationRef

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-Name Accounting Standards Codification

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Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant