Impaired Loans and Valuation Allowance for Loan Losses - Activity in Allowance for Loan Losses (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance, Beginning Balance	$ 22,104	$ 25,565	$ 37,744
Provision for Loan Losses	3,188	10,796	1,974
Charge-Offs	(6,784)	(18,288)	(16,446)
Recoveries	1,560	4,031	2,293
Net Charge-Offs	(5,224)	(14,257)	(14,153)
Allowance, Ending Balance	20,068	22,104	25,565
Construction and Land Development [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance, Beginning Balance	1,134	1,883	7,214
Provision for Loan Losses	66	(478)	(1,645)
Charge-Offs	(604)	(612)	(4,739)
Recoveries	212	341	1,053
Net Charge-Offs	(392)	(271)	(3,686)
Allowance, Ending Balance	808	1,134	1,883
Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance, Beginning Balance	8,849	11,477	18,563
Provision for Loan Losses	(522)	3,209	(3,777)
Charge-Offs	(2,714)	(8,539)	(3,663)
Recoveries	547	2,702	354
Net Charge-Offs	(2,167)	(5,837)	(3,309)
Allowance, Ending Balance	6,160	8,849	11,477
Residential Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance, Beginning Balance	11,090	10,966	10,102
Provision for Loan Losses	3,273	7,767	7,833
Charge-Offs	(3,153)	(8,381)	(7,482)
Recoveries	449	738	513
Net Charge-Offs	(2,704)	(7,643)	(6,969)
Allowance, Ending Balance	11,659	11,090	10,966
Commercial and Financial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance, Beginning Balance	468	402	480
Provision for Loan Losses	(24)	283	(379)
Charge-Offs	(60)	(346)	0
Recoveries	326	129	301
Net Charge-Offs	266	(217)	301
Allowance, Ending Balance	710	468	402
Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance, Beginning Balance	563	837	1,385
Provision for Loan Losses	395	15	(58)
Charge-Offs	(253)	(410)	(562)
Recoveries	26	121	72
Net Charge-Offs	(227)	(289)	(490)
Allowance, Ending Balance	$ 731	$ 563	$ 837