Derivatives and Hedging Activities - Derivative Instrument Cash Flow Hedge Earning Recognized by Income Statement Location (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2022	Mar. 31, 2021
Derivatives, Fair Value [Line Items]
Net Gains (Losses) Recognized in OCI	$ (658)	$ (190)
Net Gains (Losses) Reclassified From OCI Into Income	65	89
Interest income – loans \| Interest rate \| Cash Flow Hedges
Derivatives, Fair Value [Line Items]
Net Gains (Losses) Recognized in OCI	(670)	(203)
Net Gains (Losses) Reclassified From OCI Into Income	64	89
Interest expense — Long-term debt \| Interest rate \| Cash Flow Hedges
Derivatives, Fair Value [Line Items]
Net Gains (Losses) Recognized in OCI	3	3
Net Gains (Losses) Reclassified From OCI Into Income	(1)	(1)
Investment banking and debt placement fees \| Interest rate \| Cash Flow Hedges
Derivatives, Fair Value [Line Items]
Net Gains (Losses) Recognized in OCI	9	10
Net Gains (Losses) Reclassified From OCI Into Income	$ 2	$ 1

Amount, before tax and reclassification, of gain (loss) from derivative instrument designated and qualifying cash flow hedge included in assessment of hedge effectiveness.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 20
-Section 45
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=121577181&loc=SL110061190-113977

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4A
-Subparagraph (b)(2)
-URI http://asc.fasb.org/extlink&oid=125515794&loc=SL5618551-113959

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=125515794&loc=SL5624171-113959

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=124509347&loc=d3e637-108580

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 10A
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=124509347&loc=SL7669646-108580

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