Contractual Maturities of Federal Home Loan Bank Advances (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Federal Home Loan Bank, Advances, Branch of FHLB Bank [Line Items]
Within 1 year	$ 15,600	$ 11,500
1 - 2 years	1,500	12,850
Total	$ 17,100	$ 24,350