Federal Home Loan Bank Advances - Maturities of FHLB Advances Outstanding (Parenthetical) (Detail)	Sep. 30, 2012
Maturity January 2012, fixed rate 2.37% [Member]
Federal Home Loan Bank, Advances, Branch of FHLB Bank [Line Items]
Interest rates on Federal Home Loan Bank Advances	2.37%
Minimum [Member] | Maturities January 2014 through August 2014, with fixed rates ranging from 2.06% to 3.55% [Member]
Federal Home Loan Bank, Advances, Branch of FHLB Bank [Line Items]
Interest rates on Federal Home Loan Bank Advances	2.06%
Minimum [Member] | Maturities January 2015 and July 2015, with fixed rates ranging from 0.80% to 4.76% [Member]
Federal Home Loan Bank, Advances, Branch of FHLB Bank [Line Items]
Interest rates on Federal Home Loan Bank Advances	0.80%
Maximum [Member] | Maturities January 2014 through August 2014, with fixed rates ranging from 2.06% to 3.55% [Member]
Federal Home Loan Bank, Advances, Branch of FHLB Bank [Line Items]
Interest rates on Federal Home Loan Bank Advances	3.55%
Maximum [Member] | Maturities January 2015 and July 2015, with fixed rates ranging from 0.80% to 4.76% [Member]
Federal Home Loan Bank, Advances, Branch of FHLB Bank [Line Items]
Interest rates on Federal Home Loan Bank Advances	4.76%