Goodwill and Identifiable Intangible Assets - Carrying Amount of Goodwill and Intangibles (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Intangible Assets And Goodwill [Line Items]
Goodwill, Beginning Balance	$ 2,714	$ 2,714	$ 2,714
Total, Beginning Balance	4,019	3,655
Additions	708	626
Amortization Expense	(384)	(262)
Total, Ending Balance	4,343	4,019
Mortgage Servicing Rights [Member]
Intangible Assets And Goodwill [Line Items]
Beginning Balance	1,305	941
Additions	708	626
Amortization Expense	(384)	(262)
Ending Balance	$ 1,629	$ 1,305