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			6 Months Ended
	Jan. 01, 2020		Jun. 30, 2020		Jun. 30, 2019	Jun. 30, 2020		Jun. 30, 2019
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance, beginning of period	$ 1,202	[1]	$ 2,348		$ 1,115	$ 1,202	[1]	$ 1,103
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201613Member							us-gaap:AccountingStandardsUpdate201602Member
Losses charged-off			(163)		(119)	(322)		$ (228)
Recoveries of losses previously charged-off			33		41	70		72
Provision for loan and lease losses			478		78	1,103		168
Balance, end of period	$ 33		2,696	[1]	1,115	2,696	[1]	1,115
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)		(11)	(22)		(22)
Recoveries of losses previously charged-off			9		11	22		22
Commercial
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance, beginning of period	710		1,313		654	710		645
Impact of adoption of ASU 2016-13						31
Losses charged-off			(81)		(33)	(142)		(53)
Recoveries of losses previously charged-off			3		10	7		13
Provision for loan and lease losses			267		20	767		46
Balance, end of period			1,502		651	1,502		651
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		260		79	73		81
Impact of adoption of ASU 2016-13						2
Losses charged-off			(2)		(1)	(4)		(3)
Recoveries of losses previously charged-off			1		2	2		3
Provision for loan and lease losses			68		(4)	60		(5)
Balance, end of period			327		76	327		76
Initial recognition of ALLL on PCD loans			1
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		775		270	298		267
Impact of adoption of ASU 2016-13						1
Losses charged-off			(80)		(85)	(176)		(172)
Recoveries of losses previously charged-off			29		29	61		56
Provision for loan and lease losses			143		62	276		125
Balance, end of period			867		276	867		276
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
Provision for loan and lease losses			0		0	0		2
Balance, end of period			$ 0		$ 112	0		$ 112
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 $66 and $74 of other short-term investments, $1,032 and $1,354 of portfolio loans and leases, $(14) and $(7) of ALLL, $7 and $8 of other assets, $2 and $2 of other liabilities, and $933 and $1,253 of long-term debt from consolidated VIEs that are included in their respective captions above at June 30, 2020 and December 31, 2019, respectively. For further information refer to Note 13.