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Allowance for Credit Losses and Reserve for Unfunded Lending Commitments - Additional Information (Detail) $ in Millions | 3 Months Ended
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Mar. 31, 2020 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items] |
Allowance for credit loss | $ 14,073
Allowance for credit losses |
Accounts, Notes, Loans and Financing Receivable [Line Items] |
Increase (Decrease) in Allowance for Credit Loss | 6,900
Allowance for credit loss | $ 14,073

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