Additional Detail of Impaired Loans Broken Out According to Class (Detail) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
Jun. 30, 2015	Dec. 31, 2014
Financing Receivable, Impaired [Line Items]
Impaired loans with no a valuation allowance, recorded investment	$ 4,622	$ 4,702
Impaired loans with no related allowance, unpaid balance	4,622	4,702
Impaired loans with no related allowance	0	0
Impaired loans with no related allowance, average recorded investment YTD	4,743	2,894
Impaired loans with no related allowance, interest income recognized YTD	13	142
Impaired loans with a related allowance, recorded investment	4,499	4,858
Impaired loans with a related allowance, unpaid balance	4,499	4,858
Impaired loans with a related allowance	1,008	968
Impaired loans with a related allowance, average recored investment YTD	4,358	4,183
Impaired loans with a related allowance, interest income recognized YTD	57	114
Recorded Investment	9,121	9,560
Unpaid Balance	9,121	9,560
Related Allowance	1,008	968
Average Recorded Investment YTD	9,101	7,077
Interest Income Recognized YTD	70	256
Commercial installment
Financing Receivable, Impaired [Line Items]
Impaired loans with no a valuation allowance, recorded investment	0	0
Impaired loans with no related allowance, unpaid balance	0	0
Impaired loans with no related allowance	0	0
Impaired loans with no related allowance, average recorded investment YTD	2	50
Impaired loans with no related allowance, interest income recognized YTD	0	0
Impaired loans with a related allowance, recorded investment	275	240
Impaired loans with a related allowance, unpaid balance	275	240
Impaired loans with a related allowance	23	18
Impaired loans with a related allowance, average recored investment YTD	250	189
Impaired loans with a related allowance, interest income recognized YTD	7	20
Recorded Investment	275	240
Unpaid Balance	275	240
Related Allowance	23	18
Average Recorded Investment YTD	252	239
Interest Income Recognized YTD	7	20
Commercial real estate
Financing Receivable, Impaired [Line Items]
Impaired loans with no a valuation allowance, recorded investment	4,343	4,665
Impaired loans with no related allowance, unpaid balance	4,343	4,665
Impaired loans with no related allowance	0	0
Impaired loans with no related allowance, average recorded investment YTD	4,544	2,654
Impaired loans with no related allowance, interest income recognized YTD	13	142
Impaired loans with a related allowance, recorded investment	3,244	2,558
Impaired loans with a related allowance, unpaid balance	3,244	2,558
Impaired loans with a related allowance	454	315
Impaired loans with a related allowance, average recored investment YTD	2,765	2,415
Impaired loans with a related allowance, interest income recognized YTD	44	59
Recorded Investment	7,587	7,223
Unpaid Balance	7,587	7,223
Related Allowance	454	315
Average Recorded Investment YTD	7,309	5,069
Interest Income Recognized YTD	57	201
Consumer real estate
Financing Receivable, Impaired [Line Items]
Impaired loans with no a valuation allowance, recorded investment	271	27
Impaired loans with no related allowance, unpaid balance	271	27
Impaired loans with no related allowance	0	0
Impaired loans with no related allowance, average recorded investment YTD	188	179
Impaired loans with no related allowance, interest income recognized YTD	0	0
Impaired loans with a related allowance, recorded investment	953	2,032
Impaired loans with a related allowance, unpaid balance	953	2,032
Impaired loans with a related allowance	504	607
Impaired loans with a related allowance, average recored investment YTD	1,315	1,546
Impaired loans with a related allowance, interest income recognized YTD	6	33
Recorded Investment	1,224	2,059
Unpaid Balance	1,224	2,059
Related Allowance	504	607
Average Recorded Investment YTD	1,503	1,725
Interest Income Recognized YTD	6	33
Consumer installment
Financing Receivable, Impaired [Line Items]
Impaired loans with no a valuation allowance, recorded investment	8	10
Impaired loans with no related allowance, unpaid balance	8	10
Impaired loans with no related allowance	0	0
Impaired loans with no related allowance, average recorded investment YTD	9	11
Impaired loans with no related allowance, interest income recognized YTD	0	0
Impaired loans with a related allowance, recorded investment	27	28
Impaired loans with a related allowance, unpaid balance	27	28
Impaired loans with a related allowance	27	28
Impaired loans with a related allowance, average recored investment YTD	28	33
Impaired loans with a related allowance, interest income recognized YTD	0	2
Recorded Investment	35	38
Unpaid Balance	35	38
Related Allowance	27	28
Average Recorded Investment YTD	37	44
Interest Income Recognized YTD	$ 0	$ 2

Amount of allowance for credit losses related to recorded investment.

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