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Federal Funds Purchased and Securities Sold Under Agreement to Repurchase - Daily Securities Sold under Agreement to Repurchase (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Schedule of Trading Securities and Other Trading Assets [Line Items]
Amount Outstanding at End of Period	$ 25,700
Daily Securities Sold Under Agreement to Repurchase [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Amount Outstanding at End of Period	$ 806	$ 6,145
Weighted Average Rate End of Period	1.04%	1.19%
Maximum Amount Borrowings Outstanding Month End	$ 819	$ 14,929
Approximate Average Outstanding in Period	$ 1,026	$ 10,253
Approximate Weighted Average Interest Rate For the Period	1.12%	0.96%
Term CDs Sold Under Agreement to Repurchase [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Amount Outstanding at End of Period	$ 24,889	$ 22,925
Weighted Average Rate End of Period	2.00%	1.97%
Maximum Amount Borrowings Outstanding Month End	$ 24,889	$ 22,925
Approximate Average Outstanding in Period	$ 23,793	$ 21,172
Approximate Weighted Average Interest Rate For the Period	1.87%	1.81%

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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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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
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