Allowance for Loan Losses and Impaired Loans - Additional Information (Detail)		12 Months Ended
		Dec. 31, 2016 USD ($) Loan	Dec. 31, 2015 USD ($) Loan	Jul. 01, 2016 USD ($)
Financing Receivable, Allowance for Credit Losses [Line Items]
Total of outstanding loans		$ 411,968,000	$ 241,216,000	$ 402,652,000
Investment in impaired loans	[1]	13,320,000	11,239,000
Investment in impaired loans, with no related allowance	[1]	4,355,000	2,112,000
Troubled debt restructured loans		6,100,000	6,200,000
Troubled debt restructured loans, related allowance		$ 315,000	$ 317,000
Loans modified that considered to be TDRs | Loan		7	5
Unallocated Financing Receivables
Financing Receivable, Allowance for Credit Losses [Line Items]
Provision for loan losses		$ 0	$ 0
Collateral Pledged
Financing Receivable, Allowance for Credit Losses [Line Items]
Investment in impaired loans		4,000,000	1,100,000
Doubtful
Financing Receivable, Allowance for Credit Losses [Line Items]
Total of outstanding loans		0	0
Loss
Financing Receivable, Allowance for Credit Losses [Line Items]
Total of outstanding loans		0	0
Maximum
Financing Receivable, Allowance for Credit Losses [Line Items]
Troubled debt restructured loans			250,000
Impaired Loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Troubled debt restructured loans		$ 10,000,000	$ 10,700,000
Term Concessions Granted Loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Number of loans | Loan		7
Additional Funds Advanced Loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Number of loans | Loan		2
Interest Concessions Granted Loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Number of loans | Loan			2
Rate and Term Concessions Granted Loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Number of loans | Loan			3

[1] Recorded investment is the loan balance, net of any charge-offs