Goodwill and Intangible Assets (Detail) - Schedule of Customer List Intangibles (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011	Sep. 30, 2011
Gross Carrying Amount	$ 10,160	$ 3,211	$ 3,211
Accumulated Amortization	2,135	810	720
Net Carrying Amount	8,025	2,401	2,491
Customer Relationships [Member]
Gross Carrying Amount	3,211	3,211	3,211
Accumulated Amortization	1,140	810	720
Net Carrying Amount	2,071	2,401	2,491
Core Deposits [Member]
Gross Carrying Amount	6,787
Accumulated Amortization	941
Net Carrying Amount	5,846
Noncompete Agreements [Member]
Gross Carrying Amount	162
Accumulated Amortization	54
Net Carrying Amount	$ 108