Derivatives - Fair Values of Derivatives Reported on Consolidated Statements of Financial Condition (Parenthetical) (Detail) - Total Return Swaps [Member] - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Derivatives, Fair Value [Line Items]
Gross derivative assets	$ 152	$ 152
Gross derivative liability	9,797	$ 8,679
Cash collateral pledged for total return swaps	$ 6,893

Fair value, before effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities elected not to be offset. Excludes liabilities not subject to a master netting arrangement.

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