Investment Securities - Additional Information (Detail)	6 Months Ended
Jun. 30, 2020 USD ($) investment_security	Dec. 31, 2019 USD ($)
Investment Securities [Line Items]
Securities pledged as collateral	$ 479,242,000	$ 466,321,000
Residential real estate mortgage-backed securities	$ 739,470,000,000
Life of mortgage-backed securities	3 years 3 months 3 days
Asset backed securities
Investment Securities [Line Items]
Percentage of aggregate depreciation in unrealized losses	(3.58%)
Number of available for sale securities in unrealized loss position (in investment securities) \| investment_security	13

Debt securities issued by a United States government agency such as Government National Mortgage Association (Ginnie Mae), Federal Home Loan Mortgage Corporation (Freddie Mac), and Federal National Mortgage Association (Fannie Mae), which are short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify under that definition. Original maturity means original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three-years ago does not become a cash equivalent when its remaining maturity is three months.

No definition available.

Name:	us-gaap_USGovernmentAgenciesSecuritiesAtCarryingValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant