Purchase and Assumption - Assets and Liabilities of SCB Recorded at Provisional Fair Value (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended	0 Months Ended
	Dec. 31, 2012	Feb. 10, 2012 SCB Bank		Feb. 10, 2012 Non-interest bearing SCB Bank	Feb. 10, 2012 NOW accounts SCB Bank	Feb. 10, 2012 Savings and money market SCB Bank	Feb. 10, 2012 Certificate of deposit SCB Bank	Feb. 10, 2012 Commercial SCB Bank	Feb. 10, 2012 Residential Mortgage SCB Bank	Feb. 10, 2012 Installment Loans SCB Bank
Business Acquisition [Line Items]
Cash and due from banks (1)		$ 29,113	[1]
Investment securities, available for sale		18,896
Federal Home Loan Bank stock		1,761
Total Loans		93,793						51,042	11,181	31,570
Premises		1,516
Core deposit intangible		484
Other assets		560
Total Assets Purchased		146,123
Total Deposits		125,909		13,715	14,746	25,843	71,605
Federal Home Loan Bank advances		10,286
Other liabilities		804
Total Liabilities Assumed		136,999
Net Gain on Acquisition	$ 9,124	$ 9,124

[1] Includes $17,200,000 cash received from the FDIC.