Impaired Loans and Allowance for Loan Losses - Additional Information (Detail) (USD $)	3 Months Ended				12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Financing Receivable, Modifications [Line Items]
Newly identified TDRs	$ 500,000	$ 1,700,000	$ 4,100,000	$ 4,400,000	$ 10,700,000
Loan default period					60 days
Accruing TDRs	25,100,000				25,100,000	41,900,000
Average recorded investment in impaired loans					66,603,000	96,439,000	119,528,000
Interest income on impaired loans					1,260,000	3,054,000	3,541,000
Expected future cash flows of impaired loans					1,100,000	1,000,000	1,100,000
Nonaccrual loans and loans past due ninety days	27,672,000				27,672,000	40,955,000	28,526,000
Accrual Loans	160,000				160,000	1,000	0
Commercial and Financial Loan [Member]
Financing Receivable, Modifications [Line Items]
Newly identified TDRs					200,000
Consumer [Member]
Financing Receivable, Modifications [Line Items]
Newly identified TDRs					100,000
Commercial Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Newly identified TDRs					3,400,000
Average recorded investment in impaired loans					24,646,000	51,630,000
Interest income on impaired loans					423,000	1,737,000
Nonaccrual loans and loans past due ninety days	5,111,000				5,111,000	17,234,000
Residential Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Newly identified TDRs					1,400,000
Average recorded investment in impaired loans					37,411,000	38,814,000
Interest income on impaired loans					647,000	1,151,000
Nonaccrual loans and loans past due ninety days	$ 20,705,000				$ 20,705,000	$ 22,099,000