Loans - Pre-Modification and Post-Modification Outstanding Recorded Investments (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013 Contract	Mar. 31, 2012 Contract
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Contracts	32	19
Pre-Modification Outstanding Recorded Investment	$ 11,372	$ 6,546
Post-Modification Outstanding Recorded Investment	10,009	6,293
Commercial and industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Contracts	4	5
Pre-Modification Outstanding Recorded Investment	2,838	1,422
Post-Modification Outstanding Recorded Investment	1,590	1,230
Commercial real estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Contracts	5	6
Pre-Modification Outstanding Recorded Investment	4,454	2,049
Post-Modification Outstanding Recorded Investment	4,461	1,988
Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Contracts	1	2
Pre-Modification Outstanding Recorded Investment	538	2,154
Post-Modification Outstanding Recorded Investment	538	2,154
Commercial real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Contracts	6	8
Pre-Modification Outstanding Recorded Investment	4,992	4,203
Post-Modification Outstanding Recorded Investment	4,999	4,142
Residential mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Contracts	17	4
Pre-Modification Outstanding Recorded Investment	3,164	852
Post-Modification Outstanding Recorded Investment	3,091	853
Consumer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Contracts	5	2
Pre-Modification Outstanding Recorded Investment	378	69
Post-Modification Outstanding Recorded Investment	$ 329	$ 68