Fair value estimates - Summary of Assets and Liabilities Measured at Fair Value on a Nonrecurring Basis (Detail) - Fair Value Measurements Nonrecurring [Member] - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other real estate owned	$ 219	$ 422
Impaired loans, net of related allowance	5,835
Total	6,054	422
Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other real estate owned	219	422
Impaired loans, net of related allowance	5,835
Total	$ 6,054	$ 422