Variable Interest Entities - Securitization Activity (Details) - Securitization entities not consolidated - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Residential mortgage
Securitization activity [Abstract]
Principal securitized	$ 1,513	$ 1,017	$ 5,972	$ 3,066
All cash flows during the period:
Proceeds received from loan sales as financial instruments	1,524	1,053	5,984	3,136
Servicing fees collected	43	49	134	151
Purchases of previously transferred financial assets (or the underlying collateral)	0	0	0	1
Cash flows received on interests	99	125	328	384
Commercial and other
Securitization activity [Abstract]
Principal securitized	3,533	4,411	8,705	7,723
All cash flows during the period:
Proceeds received from loan sales as financial instruments	3,558	4,419	8,745	7,796
Servicing fees collected	1	1	1	3
Purchases of previously transferred financial assets (or the underlying collateral)	0	0	0	0
Cash flows received on interests	$ 99	$ 287	$ 230	$ 828

The principal amount of financial assets transferred during the period in securitizations accounted for as sales.

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- Definition

Securitization activity.

+ References

No definition available.

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- References

No definition available.

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- Definition

Cash Flows between a transferor and a transferee attributable to newly transferred assets related to either a securitization, asset-backed financing arrangement, or similar transfer in which the transferor has continuing involvement with the transferred financial assets underlying the transaction (including, but not limited to, servicing, recourse, and restrictions on transferor's interests in the transferred financial assets).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (d)(1)
-URI http://asc.fasb.org/extlink&oid=109247956&loc=d3e107207-111719

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- Definition

Cash Flows between a transferor and a transferee attributable to purchases of previously transferred financial assets (or its underlying collateral) related to a securitization, asset-backed financing arrangement, or similar transfer in which the transferor has continuing involvement with the transferred financial assets underlying the transaction (including, but not limited to, servicing, recourse, and restrictions on transferor's interests in the transferred financial assets).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (d)(3)
-URI http://asc.fasb.org/extlink&oid=109247956&loc=d3e107207-111719

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- Definition

Cash flows between transferor and a transferee attributable to the transferor's interests related to a securitization, asset-backed financing arrangement, or similar transfer in which the transferor will have continuing involvement with the transferred financial assets underlying the transaction (including, but not limited to, servicing, recourse, and restrictions on transferor's interests in the transferred financial assets).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (d)(5)
-URI http://asc.fasb.org/extlink&oid=109247956&loc=d3e107207-111719

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- Definition

Cash Flows between a transferee and a transferor attributable to servicing fees related to a securitization, asset-backed financing arrangement, or similar transfer in which the transferor has continuing involvement with the transferred financial assets underlying the transaction (including, but not limited to, servicing, recourse, and restrictions on transferor's interests in the transferred financial assets).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (d)(4)
-URI http://asc.fasb.org/extlink&oid=109247956&loc=d3e107207-111719

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