Loans - Summary of Impaired Loans (Detail) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Mortgage Loans On Real Estate [Line Items]
Total TDRs (these are included in impaired loans)	$ 11,863	$ 12,524
Impaired loans that are not TDRs	19,132	13,616
Total impaired loans, excluding PCD loans	30,995	26,140
Impaired PCD loans	22,776
Total impaired loans	53,771	26,140
Performing TDRs [Member]
Mortgage Loans On Real Estate [Line Items]
Total TDRs (these are included in impaired loans)	7,215	8,012
Non-performing TDRs [Member]
Mortgage Loans On Real Estate [Line Items]
Total TDRs (these are included in impaired loans)	$ 4,648	$ 4,512