Goodwill and Intangible Assets - Schedule of Estimated Amortization Expense (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Acquired Finite-Lived Intangible Assets [Line Items]
2019	$ 771
2020	1,001
2021	978
2022	956
2023	927
Thereafter	4,471
Net Carrying Amount	9,104	$ 9,352
MSRs [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
2019	66
2020	88
2021	87
2022	88
2023	86
Thereafter	1,241
Net Carrying Amount	1,656	1,664
Core deposit intangibles [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
2019	705
2020	913
2021	891
2022	868
2023	841
Thereafter	3,230
Net Carrying Amount	$ 7,448	$ 7,688