Investment Securities - Additional Information (Detail)	12 Months Ended
Dec. 31, 2020 USD ($) investmentSecurity	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Investment Securities [Line Items]
Credit loss	$ 0	$ 0	$ 0
Allowance for credit loss	0
Proceeds from sale of available for sale securities	229,000	127,066,000	293,279,000
Gain on sale of investment securities	7,000	110,000	$ 207,000
Realized gain		338,000
Gross realized losses		228,000
Securities pledged as collateral	429,049,000	$ 466,321,000
Residential real estate mortgage-backed securities	$ 828,047,000
Life of mortgage-backed securities	3 years 21 days
Obligations of U.S. government agencies
Investment Securities [Line Items]
Available for sale securities in unrealized loss position \| investmentSecurity	10
Percentage of aggregate depreciation in unrealized losses	0.55%
Asset backed securities
Investment Securities [Line Items]
Available for sale securities in unrealized loss position \| investmentSecurity	30
Percentage of aggregate depreciation in unrealized losses	1.46%

Investment Securities [Line Items]

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Life of mortgage backed securities.

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Percentage of aggregate depreciation in unrealized losses.

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- Definition

Securities Pledged as Collateral

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No definition available.

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- Definition

Amount of realized gain on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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- Definition

Amount of realized loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Number of investments in debt securities measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in unrealized loss position, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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Amount of allowance for credit loss for debt security measured at amortized cost (held-to-maturity).

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Amount of expense (reversal of expense) for expected credit loss on investment in debt security measured at amortized cost (held-to-maturity).

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- Definition

The difference between the carrying value and the sale price of an investment. A gain would be recognized when the sale price of the investment is greater than the carrying value of the investment. This element refers to the Gain included in earnings and not to the cash proceeds of the sale.

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Amount of cash inflow from sale of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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- Definition

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.

+ References

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