Loans (Rollforward of Allowance for Unfunded Lending Related Commitments) (Details) $ in Millions	3 Months Ended
Mar. 31, 2020 USD ($)
Off-Balance Sheet, Credit Loss, Liability [Roll Forward]
Beginning balance	$ 318
Provision for (recapture of ) credit losses	(47)
Ending balance	$ 450
Portfolio segment ACL as a percentage of total ACL for unfunded lending related commitments	100.00%
Total commercial lending
Off-Balance Sheet, Credit Loss, Liability [Roll Forward]
Beginning balance	$ 316
Provision for (recapture of ) credit losses	(25)
Ending balance	$ 344
Portfolio segment ACL as a percentage of total ACL for unfunded lending related commitments	76.00%
Total consumer lending
Off-Balance Sheet, Credit Loss, Liability [Roll Forward]
Beginning balance	$ 2
Provision for (recapture of ) credit losses	(22)
Ending balance	$ 106
Portfolio segment ACL as a percentage of total ACL for unfunded lending related commitments	24.00%

Off-Balance Sheet, Credit Loss, Liability, Percentage Of Total Allowance For Credit Credit Losses

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- Definition

Amount of expected credit loss for credit exposure on off-balance-sheet commitment, including but not limited to, loan commitment, standby letter of credit, financial guarantee not accounted for as insurance. Excludes off-balance sheet credit exposure accounted for as insurance and instrument accounted for under derivatives and hedging.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 460
-SubTopic 10
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=118956080&loc=d3e11927-110247

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=118955202&loc=SL82919202-210446

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- Definition

Amount of expense (reversal of expense) for expected credit loss for off-balance sheet credit exposure. Excludes off-balance sheet credit exposure accounted for as insurance and instrument accounted for under derivatives and hedging.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 13
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=119407570&loc=SL82919249-210447

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- References

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