Fair Value of Financial Instruments - Impaired Loans (Detail) - Collateral Dependent Impaired Loans [Member] - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Level 3 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value on a nonrecurring basis, Total	$ 4,130	$ 7,703
Fair Value on Nonrecurring Basis [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value on a nonrecurring basis, Total	4,130	7,703
Fair Value on Nonrecurring Basis [Member] | Level 3 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value on a nonrecurring basis, Total	$ 4,130	$ 7,703