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Allowance for Credit Losses and Reserve for Unfunded Lending Commitments - Additional Information (Detail) $ in Millions	3 Months Ended
	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

X

- Definition

Increase (Decrease) in Allowance for Credit Loss

+ References

No definition available.

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X

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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X

- Definition

Amount of allowance for credit loss on financing receivable. Excludes allowance for financing receivable covered under loss sharing agreement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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-Section 50
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