Loans and Loans Held for Sale - Restructured Loans for Periods Stated (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015 SecurityLoan		Mar. 31, 2014 SecurityLoan
Financing Receivable, Modifications [Line Items]
Number of Loans	20		12
Pre-Modification Outstanding Recorded Investment	$ 4,612	[1]	$ 1,808	[1]
Post-Modification Outstanding Recorded Investment	4,585	[1]	1,791	[1]
Total Difference in Recorded Investment	(27)		(17)
Principal Deferral [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	9		1
Pre-Modification Outstanding Recorded Investment	3,616	[1]	1,019	[1]
Post-Modification Outstanding Recorded Investment	3,615	[1]	1,019	[1]
Total Difference in Recorded Investment	(1)		0
Chapter 7 Bankruptcy [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	9	[2]	11	[2]
Pre-Modification Outstanding Recorded Investment	145	[1],[2]	789	[1],[2]
Post-Modification Outstanding Recorded Investment	134	[1],[2]	772	[1],[2]
Total Difference in Recorded Investment	(11)	[2]	(17)	[2]
Maturity Date Extension [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	2
Pre-Modification Outstanding Recorded Investment	851	[1]
Post-Modification Outstanding Recorded Investment	836	[1]
Total Difference in Recorded Investment	(15)
Commercial Real Estate [Member] | Principal Deferral [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	2
Pre-Modification Outstanding Recorded Investment	2,851	[1]
Post-Modification Outstanding Recorded Investment	2,851	[1]
Total Difference in Recorded Investment	0
Commercial and Industrial [Member] | Principal Deferral [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	6
Pre-Modification Outstanding Recorded Investment	661	[1]
Post-Modification Outstanding Recorded Investment	661	[1]
Total Difference in Recorded Investment	0
Commercial and Industrial [Member] | Chapter 7 Bankruptcy [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	1	[2]	1	[2]
Pre-Modification Outstanding Recorded Investment	3	[1],[2]	287	[1],[2]
Post-Modification Outstanding Recorded Investment	1	[1],[2]	286	[1],[2]
Total Difference in Recorded Investment	(2)	[2]	(1)	[2]
Commercial and Industrial [Member] | Maturity Date Extension [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	1
Pre-Modification Outstanding Recorded Investment	780	[1]
Post-Modification Outstanding Recorded Investment	765	[1]
Total Difference in Recorded Investment	(15)
Commercial Construction [Member] | Principal Deferral [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	1		1
Pre-Modification Outstanding Recorded Investment	104	[1]	1,019	[1]
Post-Modification Outstanding Recorded Investment	103	[1]	1,019	[1]
Total Difference in Recorded Investment	(1)		0
Residential Mortgage [Member] | Interest Rate Reduction [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	4	[2]
Pre-Modification Outstanding Recorded Investment	277	[1],[2]
Post-Modification Outstanding Recorded Investment	276	[1],[2]
Total Difference in Recorded Investment	(1)	[2]
Home Equity [Member] | Chapter 7 Bankruptcy [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	8	[2]	6	[2]
Pre-Modification Outstanding Recorded Investment	142	[1],[2]	225	[1],[2]
Post-Modification Outstanding Recorded Investment	133	[1]	210	[1],[2]
Total Difference in Recorded Investment	(9)	[2]	(15)	[2]
Home Equity [Member] | Maturity Date Extension [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	1
Pre-Modification Outstanding Recorded Investment	71	[1]
Post-Modification Outstanding Recorded Investment	71	[1]
Total Difference in Recorded Investment	$ 0

[1] Excludes loans that were fully paid off or fully charged-off by period end. The pre-modification balance represents the balance outstanding prior to modification. The post-modification balance represents the outstanding balance at period end.

[2] Chapter 7 bankruptcy loans where the debt has been legally discharged through the bankruptcy court and not reaffirmed.