Loans and the Allowance for Credit Losses - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2014 Contract SecurityLoan	Dec. 31, 2013
Financing Receivable, Recorded Investment [Line Items]
Deferred loan fees and costs	$ 2.8	$ 2.7
Non-accrual status period	90 days
Number of restructured contracts greater than $1 million	0
Accruing and non accrual TDR permitted interest only payment period	3 months
Percentage of TDRs defaulted during the period that were restructured within the last twelve months	1.20%
Loans with accruing interest	0
Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Aggregate amount of residential real estate, home equity and consumer loans classified as substandard	14.7	14.4
Internally assigned loan grades to residential real estate, home equity and consumer loans	$ 2.7	$ 2.0