Summary of Significant Accounting Policies - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Significant Accounting Policies [Line Items]
Total of the average daily required reserve	$ 14,000,000	$ 12,200,000
Carrying amount of bank owned real estate	3,600,000	3,600,000
Company stock-based compensation cost	1,000,000	785,000	724,000
Cash flow for the purpose of converting floating rate loans to a fixed rate			35,000,000
Fair value	3,000,000	2,000,000
Junior Subordinated Debt [Member]
Significant Accounting Policies [Line Items]
Cash flow for the purpose of converting floating rate loans to a fixed rate	$ 37,100,000	$ 37,100,000
Contingently Issuable Shares [Member]
Significant Accounting Policies [Line Items]
Anti Dilutive Common shares excluded	418,000	414,000	628,000
Building [Member]
Significant Accounting Policies [Line Items]
Estimated lives for buildings		40 years
Minimum [Member]
Significant Accounting Policies [Line Items]
Intangible assets amortized over an estimated useful life		3 years
Minimum [Member] | Furniture and equipment [Member]
Significant Accounting Policies [Line Items]
Estimated lives for buildings		3 years
Minimum [Member] | Software and computer related equipment [Member]
Significant Accounting Policies [Line Items]
Estimated lives for buildings		3 years
Maximum [Member]
Significant Accounting Policies [Line Items]
Intangible assets amortized over an estimated useful life		10 years
Maximum [Member] | Furniture and equipment [Member]
Significant Accounting Policies [Line Items]
Estimated lives for buildings		20 years
Maximum [Member] | Software and computer related equipment [Member]
Significant Accounting Policies [Line Items]
Estimated lives for buildings		5 years