Composition of Federal Home Loan Bank Advances (Detail) (USD $) In Thousands, unless otherwise specified	9 Months Ended	12 Months Ended
	Sep. 30, 2012	Dec. 31, 2011
Federal Home Loan Bank, Advances, Branch of FHLB Bank [Line Items]
FHLB Advances	$ 17,100	$ 24,350
Weighted interest rate	3.31%	3.33%
Average balances for the period ended,
Outstanding balance	31,290	28,088
Interest Rate	2.50%	3.33%
Maximum month-end outstanding	$ 67,850	$ 32,767