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

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Name:	us-gaap_FinancingReceivableAllowanceForCreditLosses
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Allowance for Credit Losses - Narrative (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020	Dec. 31, 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan and lease losses	$ 914	$ 963	$ 444	$ 307
COVID-19 Deferrals
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan and lease losses	$ 1	$ 1