Loans and the Allowance for Credit Losses - TDRs Defaulted Later Restructured (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended	6 Months Ended
	Jun. 30, 2013 Defaults	Jun. 30, 2014 Defaults	Jun. 30, 2013 Defaults
Financing Receivable, Modifications [Line Items]
Number of Defaults	6	4	31
Recorded Investment	$ 333	$ 236	$ 2,748
Commercial Real Estate - Improved Property [Member]
Financing Receivable, Modifications [Line Items]
Number of Defaults			2
Recorded Investment			645
Commercial Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Number of Defaults			2
Recorded Investment			645
Commercial and Industrial [Member]
Financing Receivable, Modifications [Line Items]
Number of Defaults			3
Recorded Investment			313
Residential Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Number of Defaults	5	4	19
Recorded Investment	312	236	1,634
Home Equity [Member]
Financing Receivable, Modifications [Line Items]
Number of Defaults	1		6
Recorded Investment	21		124
Consumer [Member]
Financing Receivable, Modifications [Line Items]
Number of Defaults			1
Recorded Investment			$ 32