Loans - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Accounts, Notes, Loans and Financing Receivable [Line Items]
Balances of loans due from related Parties	$ 76,600,000	$ 65,000,000
Changes in New Loans	138,400,000
Changes in Affiliates Loans	126,500,000
Changes in directors and affiliates loans	300,000
Interest that would have been recognized on nonaccrual loans	7,800,000	4,900,000	5,700,000
Interest recovered on nonaccrual loans	2,600,000	1,100,000	1,000,000
Non-Accrual Loans	137,615,000	103,270,000
Troubled Debt Restructuring	32,200,000
Total Restructured Loans		18,100,000
Commercial substandard understated		91,600,000
Minimum Bank Portfolio loan need to be reviewed	500,000
Accruing Loans Period	90 days
Loans held for sale	50,605,000	72,378,000
Problem Commercial loans held for sale	3,600,000
Mortgage loans held for sale	47,000,000
Restructured Commercial Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Accrual Loans	$ 30,300,000
Minimum [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Period within which bank Loan reviewed	12 months
Maximum [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Period within which bank Loan reviewed	18 months