Derivatives - Summary of Interest Rate Swap Transactions (Detail) - USD ($)	Sep. 30, 2021	Dec. 31, 2020
Derivatives Fair Value [Line Items]
Net Exposure, Notional Amount	$ 0	$ 0
Net Exposure, Fair value	0	(64,000)
Derivative Financial Instruments, Assets [Member] | Swap Assets [Member]
Derivatives Fair Value [Line Items]
Net Exposure, Notional Amount	239,230,000	244,748,000
Net Exposure, Fair value	12,858,000	21,700,000
Derivative Financial Instruments, Liabilities [Member] | Swap Liabilities [Member]
Derivatives Fair Value [Line Items]
Net Exposure, Notional Amount	(239,230,000)	(244,748,000)
Net Exposure, Fair value	$ (12,858,000)	$ (21,764,000)