Purchase and Assumption - Additional Information (Detail) (SCB Bank [Member], USD $)	Feb. 10, 2012
SCB Bank [Member]
Business Acquisition [Line Items]
Assets Acquired	$ 147,700,000
Cash and cash equivalents	11,900,000
Marketable securities	18,896,000
Federal Home Loan Bank stock	1,800,000
Acquired loan portfolio	113,000,000
Premises and other assets	2,100,000
Liabilities absorbed	135,700,000
Customer deposits	125,900,000
Other Borrowed money	9,600,000
Other Liabilities	402,000
Assets acquired, discount	29,000,000
Difference between the purchase price of the assets acquired and the value of the liabilities assumed	17,200,000
Loan portfolio acquired, fair value discount	19,200,000
Performing portion of the acquired loan portfolio	86,300,000
Performing portion of loan portfolio, fair value	$ 76,500,000