Investment Securities Available for Sale - Summary of Credit Quality of Loans and Gross Realized Gains and Losses (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended	9 Months Ended
Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2011
Schedule of Available-for-sale Securities [Line Items]
Public funds deposits	$ 102,477		$ 102,477		$ 119,123
Federal Reserve line of credit	1,592		1,592		5,510
FHLB advances					15,887
Total	104,069		104,069		140,520
Realized gains			9,863	56
Realized losses			(4)
Net realized gains			$ 9,859	$ 56

Amount of federal home loan bank advances. Advances are loans from the federal home loan bank system to a member (shareholder).

+ References+ Details

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

+ References+ Details