Allowance for Loan Losses - Summary of Troubled Debt Restructurings (Detail) $ in Thousands		12 Months Ended
		Dec. 31, 2016 USD ($) Loan	Dec. 31, 2015 USD ($) Loan
Residential First Mortgages
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Loans | Loan	[1],[2]	1	2
Pre-Modification Outstanding Recorded Investment	[1],[2]	$ 244	$ 988
Post-Modification Outstanding Recorded Investment	[1],[2]	$ 244	$ 986
Commercial Mortgages (Owner Occupied)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Loans | Loan	[1]		1
Pre-Modification Outstanding Recorded Investment	[1]		$ 105
Post-Modification Outstanding Recorded Investment	[1]		$ 124
Subsequently defaulted number of loans | Loan			1
Subsequently defaulted recorded investment			$ 124

[1] Modifications were an extention of the loan terms.

[2] Modifications were capitalization of the interest.