Loans and Related Allowance for Credit Losses (Subsequently Defaulted TDRs) (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
TDRs [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Recorded Investment - Subsequently defaulted TDRs	$ 22	$ 28	$ 37	$ 39

Amount of financing receivable modified as troubled debt restructuring within previous 12 months, with subsequent payment default.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 34
-Subparagraph (a)(2)
-URI http://asc.fasb.org/extlink&oid=118936363&loc=SL6953682-111524

Name:	us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration