Credit Quality Assessment - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Accounts, Notes, Loans and Financing Receivable [Line Items]
Restructured Accuring Loan	$ 3.4	$ 4.9
Restructured Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Specific allowance	0.3	1.2
Restructured accruing	9.5	10.1
Restructured non-accruing	10.5	9.9
Financing Receivable Troubled Debt Restructurings Restructured Total	20.0	20.0
Other real estate owned	1.3	5.9
Additional Financing Receivable Troubled Debt Restructurings Restructured	$ 5.5	$ 5.1