Impaired Loans (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Commercial
Financing Receivable, Impaired [Line Items]
Recorded Balance	$ 1		$ 1		$ 57
Unpaid Principal Balance	1		1		123
Specific Allowance	0		0		9
Average Investment in Impaired Loans	1	$ 100	1	$ 102
Interest Income Recognized	0	2	0	4
Commercial real estate
Financing Receivable, Impaired [Line Items]
Recorded Balance	1,368		1,368		1,273
Unpaid Principal Balance	1,368		1,368		1,425
Specific Allowance	278		278		172
Average Investment in Impaired Loans	1,973	2,421	1,986	2,445
Interest Income Recognized	15	20	34	44
Residential
Financing Receivable, Impaired [Line Items]
Recorded Balance	0		0		80
Unpaid Principal Balance	0		0		203
Specific Allowance	0		0		0
Average Investment in Impaired Loans	0	0	0	0
Interest Income Recognized	0	0	0	0
Installment
Financing Receivable, Impaired [Line Items]
Recorded Balance	0		0		0
Unpaid Principal Balance	0		0		0
Specific Allowance	0		0		0
Average Investment in Impaired Loans	0	0	0	0
Interest Income Recognized	2	0	2	0
Loans without a specific valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Balance	472		472		588
Unpaid Principal Balance	472		472		741
Specific Allowance	0		0		0
Average Investment in Impaired Loans	876	1,493	885	1,500
Interest Income Recognized	9	17	17	26
Loans without a specific valuation allowance | Commercial
Financing Receivable, Impaired [Line Items]
Recorded Balance	1		1		44
Unpaid Principal Balance	1		1		74
Specific Allowance	0		0		0
Average Investment in Impaired Loans	1	0	1	0
Interest Income Recognized	0	0	0	0
Loans without a specific valuation allowance | Commercial real estate
Financing Receivable, Impaired [Line Items]
Recorded Balance	471		471		464
Unpaid Principal Balance	471		471		464
Specific Allowance	0		0		0
Average Investment in Impaired Loans	875	1,493	884	1,500
Interest Income Recognized	9	17	17	26
Loans without a specific valuation allowance | Residential
Financing Receivable, Impaired [Line Items]
Recorded Balance	0		0		80
Unpaid Principal Balance	0		0		203
Specific Allowance	0		0		0
Average Investment in Impaired Loans	0	0	0	0
Interest Income Recognized	0	0	0	0
Loans without a specific valuation allowance | Installment
Financing Receivable, Impaired [Line Items]
Recorded Balance	0		0		0
Unpaid Principal Balance	0		0		0
Specific Allowance	0	0	0	0
Average Investment in Impaired Loans	0	0	0	0
Interest Income Recognized	0	0	0	0
Loans with a specific valuation allowance
Financing Receivable, Impaired [Line Items]
Recorded Balance	897		897		822
Unpaid Principal Balance	897		897		1,010
Specific Allowance	278		278		181
Average Investment in Impaired Loans	1,098	1,028	1,102	1,047
Interest Income Recognized	8	5	19	22
Loans with a specific valuation allowance | Commercial
Financing Receivable, Impaired [Line Items]
Recorded Balance	0		0		13
Unpaid Principal Balance	0		0		49
Specific Allowance	0		0		9
Average Investment in Impaired Loans	0	100	0	102
Interest Income Recognized	0	2	0	4
Loans with a specific valuation allowance | Commercial real estate
Financing Receivable, Impaired [Line Items]
Recorded Balance	897		897		809
Unpaid Principal Balance	897		897		961
Specific Allowance	278		278		172
Average Investment in Impaired Loans	1,098	928	1,102	945
Interest Income Recognized	6	3	17	18
Loans with a specific valuation allowance | Residential
Financing Receivable, Impaired [Line Items]
Recorded Balance	0		0		0
Unpaid Principal Balance	0		0		0
Specific Allowance	0		0		0
Average Investment in Impaired Loans	0	0	0	0
Interest Income Recognized	0	0	0	0
Loans with a specific valuation allowance | Installment
Financing Receivable, Impaired [Line Items]
Recorded Balance	0		0		0
Unpaid Principal Balance	0		0		0
Specific Allowance	0		0		$ 0
Average Investment in Impaired Loans	0	0	0	0
Interest Income Recognized	$ 2	$ 0	$ 2	$ 0