Represents the caption on the face of the balance sheet to indicate that the entity has entered into (1) purchase or supply arrangements that will require expending a portion of its resources to meet the terms thereof, and (2) is exposed to potential losses or, less frequently, gains, arising from (a) possible claims against a company's resources due to future performance under contract terms, and (b) possible losses or likely gains from uncertainties that will ultimately be resolved when one or more future events that are deemed likely to occur do occur or fail to occur.

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Fair values as of the balance sheet date of all assets resulting from contracts that meet the criteria of being accounted for as derivative instruments, net of the effects of master netting arrangements.

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- Definition

The amount of net gains and losses recognized in income during the period on derivative instruments designated and qualifying as hedging instruments in fair value hedges and related hedged items designated and qualifying in fair value hedges, on derivative instruments designated and qualifying as hedging instruments in cash flow hedges, and on derivative instruments not designated as hedging instruments.

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- Definition

Fair values as of the balance sheet date of all liabilities resulting from contracts that meet the criteria of being accounted for as derivative instruments, net of the effects of master netting arrangements.

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Derivative Financial Instruments and Hedging Activities - Additional Information (Detail) (USD $)							3 Months Ended					3 Months Ended
	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2013 Loan Origination Commitments [Member]	Dec. 31, 2012 Loan Origination Commitments [Member]	Mar. 31, 2013 Loan Origination Commitments [Member] Other Assets [Member]	Dec. 31, 2012 Loan Origination Commitments [Member] Other Assets [Member]	Mar. 31, 2013 Loan Origination Commitments [Member] Sales [Member]	Dec. 31, 2012 Loan Origination Commitments [Member] Sales [Member]	Mar. 31, 2013 Forward Sales Commitment [Member]	Dec. 31, 2012 Forward Sales Commitment [Member]	Dec. 31, 2012 Forward Sales Commitment [Member] Other Assets [Member]	Mar. 31, 2013 Forward Sales Commitment [Member] Sales [Member]	Mar. 31, 2012 Forward Sales Commitment [Member] Sales [Member]	Mar. 31, 2013 Forward Sales Commitment [Member] Other Liabilities [Member]	Dec. 31, 2012 Forward Sales Commitment [Member] Other Liabilities [Member]
Derivatives, Fair Value [Line Items]
Commitments to originate conforming loans			$ 12,800,000	$ 11,100,000					$ 13,700,000	$ 11,800,000
Other assets in the Consolidated Balance Sheets	350,000	370,000			350,000	338,000					33,000
Net change in forward sales commitment fair values							13,000	48,000				(89,000)	60,000
Other liabilities in the Consolidated Balance Sheets	$ 61,000	$ 5,000												$ 61,000	$ 5,000