Loans and Loans Held for Sale - Restructured Loans for Periods Stated (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014 SecurityLoan	Dec. 31, 2013 SecurityLoan
Financing Receivable, Modifications [Line Items]
Financing Receivable, Decrease, Forgiveness		$ 100,000
Number of Loans	44	71
Pre-Modification Outstanding Recorded Investment	4,949,000	11,779,000
Post-Modification Outstanding Recorded Investment	4,777,000	11,018,000
Total Difference in Recorded Investment	172,000	(761,000)
Principal Deferral [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	6	9
Pre-Modification Outstanding Recorded Investment	2,372,000	3,769,000
Post-Modification Outstanding Recorded Investment	2,321,000	3,298,000
Total Difference in Recorded Investment	51,000	(471,000)
Interest Rate Reduction and Maturity Date Extension [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	2	2
Pre-Modification Outstanding Recorded Investment	96,000	664,000
Post-Modification Outstanding Recorded Investment	95,000	636,000
Total Difference in Recorded Investment	1,000	(28,000)
Principal Forgiveness [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans		1
Pre-Modification Outstanding Recorded Investment		4,339,000
Post-Modification Outstanding Recorded Investment		4,216,000
Total Difference in Recorded Investment		(123,000)
Chapter 7 Bankruptcy [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	29	56
Pre-Modification Outstanding Recorded Investment	1,113,000	1,983,000
Post-Modification Outstanding Recorded Investment	1,039,000	1,856,000
Total Difference in Recorded Investment	74,000	(127,000)
Maturity Date Extension [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	7	2
Pre-Modification Outstanding Recorded Investment	1,368,000	970,000
Post-Modification Outstanding Recorded Investment	1,322,000	958,000
Total Difference in Recorded Investment	46,000	(12,000)
Interest Rate Reduction [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans		1
Pre-Modification Outstanding Recorded Investment		54,000
Post-Modification Outstanding Recorded Investment		54,000
Total Difference in Recorded Investment		0
Commercial Real Estate [Member] | Principal Deferral [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	4	4
Pre-Modification Outstanding Recorded Investment	1,991,000	2,772,000
Post-Modification Outstanding Recorded Investment	1,965,000	2,494,000
Total Difference in Recorded Investment	26,000	(278,000)
Commercial Real Estate [Member] | Interest Rate Reduction and Maturity Date Extension [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans		2
Pre-Modification Outstanding Recorded Investment		664,000
Post-Modification Outstanding Recorded Investment		636,000
Total Difference in Recorded Investment		(28,000)
Commercial Real Estate [Member] | Principal Forgiveness [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans		1
Pre-Modification Outstanding Recorded Investment		4,339,000
Post-Modification Outstanding Recorded Investment		4,216,000
Total Difference in Recorded Investment		(123,000)
Commercial Real Estate [Member] | Chapter 7 Bankruptcy [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans		6
Pre-Modification Outstanding Recorded Investment		227,000
Post-Modification Outstanding Recorded Investment		190,000
Total Difference in Recorded Investment		(37,000)
Commercial Real Estate [Member] | Maturity Date Extension [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans		1
Pre-Modification Outstanding Recorded Investment		219,000
Post-Modification Outstanding Recorded Investment		219,000
Total Difference in Recorded Investment		0
Commercial and Industrial [Member] | Principal Deferral [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	2	2
Pre-Modification Outstanding Recorded Investment	381,000	670,000
Post-Modification Outstanding Recorded Investment	356,000	638,000
Total Difference in Recorded Investment	25,000	(32,000)
Commercial and Industrial [Member] | Chapter 7 Bankruptcy [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans		1
Pre-Modification Outstanding Recorded Investment		3,000
Post-Modification Outstanding Recorded Investment		1,000
Total Difference in Recorded Investment		(2,000)
Commercial and Industrial [Member] | Maturity Date Extension [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans		1
Pre-Modification Outstanding Recorded Investment		751,000
Post-Modification Outstanding Recorded Investment		739,000
Total Difference in Recorded Investment		(12,000)
Commercial Construction [Member] | Maturity Date Extension [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	1
Pre-Modification Outstanding Recorded Investment	1,019,000
Post-Modification Outstanding Recorded Investment	974,000
Total Difference in Recorded Investment	45,000
Residential Mortgage [Member] | Principal Deferral [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans		2
Pre-Modification Outstanding Recorded Investment		153,000
Post-Modification Outstanding Recorded Investment		149,000
Total Difference in Recorded Investment		(4,000)
Residential Mortgage [Member] | Chapter 7 Bankruptcy [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	9	8
Pre-Modification Outstanding Recorded Investment	651,000	617,000
Post-Modification Outstanding Recorded Investment	634,000	592,000
Total Difference in Recorded Investment	17,000	(25,000)
Residential Mortgage [Member] | Interest Rate Reduction [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans		1
Pre-Modification Outstanding Recorded Investment		54,000
Post-Modification Outstanding Recorded Investment		54,000
Home Equity [Member] | Principal Deferral [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans		1
Pre-Modification Outstanding Recorded Investment		174,000
Post-Modification Outstanding Recorded Investment		17,000
Total Difference in Recorded Investment		(157,000)
Home Equity [Member] | Interest Rate Reduction and Maturity Date Extension [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	2
Pre-Modification Outstanding Recorded Investment	96,000
Post-Modification Outstanding Recorded Investment	95,000
Total Difference in Recorded Investment	1,000
Home Equity [Member] | Chapter 7 Bankruptcy [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	15	30
Pre-Modification Outstanding Recorded Investment	432,000	1,032,000
Post-Modification Outstanding Recorded Investment	382,000	982,000
Total Difference in Recorded Investment	50,000	(50,000)
Home Equity [Member] | Maturity Date Extension [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	6
Pre-Modification Outstanding Recorded Investment	349,000
Post-Modification Outstanding Recorded Investment	348,000
Total Difference in Recorded Investment	1,000
Installment and Other Consumer [Member] | Chapter 7 Bankruptcy [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	5	11
Pre-Modification Outstanding Recorded Investment	30,000	104,000
Post-Modification Outstanding Recorded Investment	23,000	91,000
Total Difference in Recorded Investment	$ 7,000	$ (13,000)