Federal Funds Purchased and Securities Sold Under Agreements to Repurchase - Schedule of Remaining Contractual Maturity in Repurchase Agreements (Detail) - USD ($)	Sep. 30, 2020	Dec. 31, 2019
Assets Sold under Agreements to Repurchase [Line Items]
Federal funds purchased	$ 0	$ 17,843,000
Repurchase agreements, Remaining contractual maturity of the agreements	29,900,000	30,200,000
Total	29,859,000	48,073,000
Overnight & Continuous [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Federal funds purchased		17,843,000
Total	1,540,000	19,657,000
30-90 Days [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Total		3,965,000
Greater Than 90 Days [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Total	28,319,000	24,451,000
US Treasury & Agency Securities [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Repurchase agreements, Remaining contractual maturity of the agreements	29,859,000	30,230,000
US Treasury & Agency Securities [Member] \| Overnight & Continuous [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Repurchase agreements, Remaining contractual maturity of the agreements	1,540,000	1,814,000
US Treasury & Agency Securities [Member] \| 30-90 Days [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Repurchase agreements, Remaining contractual maturity of the agreements		3,965,000
US Treasury & Agency Securities [Member] \| Greater Than 90 Days [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Repurchase agreements, Remaining contractual maturity of the agreements	$ 28,319,000	$ 24,451,000

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- Definition

Amount of short term borrowing where a bank borrows, at the federal funds rate, from another bank.

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Amount after offset of short term borrowing where a bank borrows, at the federal funds rate, from another bank and securities that an entity sells and agrees to repurchase at a specified date for a specified price.

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- Definition

Amount, after the effects of master netting arrangements, of funds outstanding borrowed in the form of a security repurchase agreement between the entity and another party for the sale and repurchase of identical or substantially the same securities at a date certain for a specified price. Includes liabilities not subject to a master netting arrangement and not elected to be offset.

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