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Derivative Instruments and Hedging Activities - Cumulative Basis Adjustment for Fair Value Hedges (Detail) - AFS debt securities
$ in Thousands
Dec. 31, 2020
USD ($)
Derivative Instruments and Hedging Activities Disclosures [Line Items]  
Amortized Cost $ 272,159
Cumulative Amount of Fair Value Hedging Adjustment to Hedged Items $ 741