Accounting and Reporting Developments (Additional Information) (Detail) - USD ($) $ in Millions	Jan. 01, 2020	Mar. 31, 2020	Dec. 31, 2019
Impact of cumulative effect of change in accounting principles		$ 17,677	$ 18,315
Loans And Leases Receivable Impaired Carrying Value		$ 1
ASU 2016-13 \| Retained Earnings
ALLL and reserve for unfunded commitments	$ 653
Impact of cumulative effect of change in accounting principles	472
Allowance for loan and lease losses	$ 33

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

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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Name:	us-gaap_FinancingReceivableAllowanceForCreditLosses
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant