Other Borrowings - Summary of Other Borrowings (Parenthetical) (Detail)	Dec. 31, 2011
ConvertibleAdvanceTwo [Member]
Federal Home Loan Bank Borrowings By Year Of Maturity And Applicable Interest Rate [Line Items]
Federal Home Loan Bank Advances effective weighted-average rate	1.05%
Maturity period of Federal Home Loan Bank advances	March 2013
FixedRateAdvanceOne [Member]
Federal Home Loan Bank Borrowings By Year Of Maturity And Applicable Interest Rate [Line Items]
Federal Home Loan Bank Advances effective weighted-average rate	1.05%
Maturity period of Federal Home Loan Bank advances	April 2016
FixedRateAdvanceTwo [Member]
Federal Home Loan Bank Borrowings By Year Of Maturity And Applicable Interest Rate [Line Items]
Federal Home Loan Bank Advances effective weighted-average rate	1.05%
Maturity period of Federal Home Loan Bank advances	April 2016