Loans - Collateral-Dependent Loans (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Consumer Loans [Member] \| Residential Mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Collateral-dependent loans	$ 817	$ 803
Commercial Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Collateral-dependent loans	$ 456	$ 227

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.

No definition available.

Name:	us-gaap_AccountsNotesAndLoansReceivableLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration