Advances from Federal Home Loan Bank (Parenthetical) (Detail)	Dec. 31, 2012	Dec. 31, 2011
Federal Home Loan Bank, Advances, Branch of FHLB Bank [Line Items]
Federal Home Loan Bank advances, minimum fixed interest rates	0.91%	0.91%
Federal Home Loan Bank advances, maximum fixed interest rates	4.70%	4.81%
Federal Home Loan Bank advances, average stated rate	2.67%	3.09%
Minimum
Federal Home Loan Bank, Advances, Branch of FHLB Bank [Line Items]
Federal Home Loan Bank advances, maturity period	2014-01	2012-09
Maximum
Federal Home Loan Bank, Advances, Branch of FHLB Bank [Line Items]
Federal Home Loan Bank advances, maturity period	2017-12	2018-02