Credit Quality and the Allowance for Loan and Lease Losses - Summary of Transactions in the ALLL by Portfolio Segment (Details) - USD ($) $ in Millions			3 Months Ended			9 Months Ended
	Jan. 01, 2020		Sep. 30, 2020		Sep. 30, 2019	Sep. 30, 2020		Sep. 30, 2019
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance, beginning of period	$ 1,202	[1]	$ 2,696		$ 1,115	$ 1,202	[1]	$ 1,103
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201613Member					us-gaap:AccountingStandardsUpdate201613Member		us-gaap:AccountingStandardsUpdate201602Member
Losses charged-off			(135)		(130)	$ (457)		$ (358)
Recoveries of losses previously charged-off			34		31	104		102
(Benefit from) provision for loan and lease losses			(21)		127	1,082		296
Balance, end of period	$ 33		2,574	[1]	1,143	2,574	[1]	1,143
Cumulative Effect, Period of Adoption, Adjustment
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Impact of adoption of ASU 2016-13						643
Other Consumer Loans, Point of Sale
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Losses charged-off			(9)		(12)	(31)		(35)
Recoveries of losses previously charged-off			9		12	31		35
Commercial
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance, beginning of period	710		1,502		651	710		645
Impact of adoption of ASU 2016-13						31
Losses charged-off			(66)		(34)	(209)		(87)
Recoveries of losses previously charged-off			5		1	14		14
(Benefit from) provision for loan and lease losses			92		53	858		99
Balance, end of period			1,533		671	1,533		671
Commercial | Cumulative Effect, Period of Adoption, Adjustment
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Impact of adoption of ASU 2016-13						160
Residential Mortgage
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance, beginning of period	73		327		76	73		81
Impact of adoption of ASU 2016-13						2
Losses charged-off			(1)		(2)	(6)		(5)
Recoveries of losses previously charged-off			2		1	5		4
(Benefit from) provision for loan and lease losses			(31)		0	29		(5)
Balance, end of period			297		75	297		75
Residential Mortgage | Cumulative Effect, Period of Adoption, Adjustment
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Impact of adoption of ASU 2016-13						196
Consumer
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance, beginning of period	298		867		276	298		267
Impact of adoption of ASU 2016-13						1
Losses charged-off			(68)		(94)	(242)		(266)
Recoveries of losses previously charged-off			27		29	85		84
(Benefit from) provision for loan and lease losses			(82)		72	195		198
Balance, end of period			744		283	744		283
Consumer | Cumulative Effect, Period of Adoption, Adjustment
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Impact of adoption of ASU 2016-13						408
Unallocated
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance, beginning of period	$ 121		0		112	121		110
Losses charged-off			0		0	0		0
Recoveries of losses previously charged-off			0		0	0		0
(Benefit from) provision for loan and lease losses			0		2	0		4
Balance, end of period			$ 0		$ 114	0		$ 114
Unallocated | Cumulative Effect, Period of Adoption, Adjustment
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Impact of adoption of ASU 2016-13						$ (121)

[1] Includes $61 and $74 of other short-term investments, $887 and $1,354 of portfolio loans and leases, $(9) and $(7) of ALLL, $5 and $8 of other assets, $2 and $2 of other liabilities, and $786 and $1,253 of long-term debt from consolidated VIEs that are included in their respective captions above at September 30, 2020 and December 31, 2019, respectively. For further information refer to Note 13.