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Derivative Financial Instruments - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Jun. 30, 2019
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Amount of collateral posted for the net assets/liability positions	$ 2,310,000		$ 2,310,000
Not Designated as Hedging Instrument [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivatives recorded gains (losses) during the period	$ 187,000	$ 51,000	$ 331,000	$ 94,000
Interest Rate Swaps/Derivatives [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Reclassification from accumulated other comprehensive income (loss) as increase to interest income					$ 111,000
Reclassification from accumulated other comprehensive income, time period			12 months