Credit Quality and the Allowance for Loan and Lease Losses - Summary of the ALLL and Related Loans and Leases Classified by Portfolio Segment (Details) - USD ($) $ in Millions		Jun. 30, 2021		Mar. 31, 2021	Dec. 31, 2020		Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually evaluated		$ 194			$ 225
Collectively evaluated		1,839			2,228
Total ALLL		2,033	[1]	$ 2,208	2,453	[1]	$ 2,696	$ 2,348	$ 1,202
Individually evaluated		1,463			1,863
Collectively evaluated		106,119			106,343
Purchased credit deteriorated					415
Total portfolio loans and leases		107,582			108,621
Leveraged leases		311			323
Total	[1],[2]	107,733			108,782
Residential mortgage loans | GNMA loans
Financing Receivable, Allowance for Credit Loss [Line Items]
Total					39
Commercial Leveraged Leases
Financing Receivable, Allowance for Credit Loss [Line Items]
Total ALLL		3			3
Leveraged leases		311			323
Commercial
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually evaluated		101			114
Collectively evaluated		1,123			1,342
Total ALLL		1,224		1,329	1,456		1,502	1,313	710
Individually evaluated		629			962
Collectively evaluated		66,391			67,701
Purchased credit deteriorated					334
Total portfolio loans and leases		67,020			68,997
Total		67,020			68,997
Residential Mortgage
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually evaluated		55			68
Collectively evaluated		180			226
Total ALLL		235		247	294		327	260	73
Individually evaluated		539			628
Collectively evaluated		15,441			15,073
Purchased credit deteriorated					66
Total portfolio loans and leases		15,980			15,767
Residential mortgage loans		151			161		185
Residential Mortgage | Residential mortgage loans
Financing Receivable, Allowance for Credit Loss [Line Items]
Total		15,980			15,767
Consumer
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually evaluated		38			43
Collectively evaluated		536			660
Total ALLL		574		$ 632	703		$ 867	$ 775	$ 298
Individually evaluated		295			273
Collectively evaluated		24,287			23,569
Purchased credit deteriorated					15
Total portfolio loans and leases		24,582			23,857
Total		$ 40,713			39,785
Consumer | Residential mortgage loans | GNMA loans
Financing Receivable, Allowance for Credit Loss [Line Items]
Total					$ 39

[1] Includes $33 and $55 of other short-term investments, $455 and $756 of portfolio loans and leases, $(3) and $(7) of ALLL, $3 and $5 of other assets, $1 and $2 of other liabilities, and $400 and $656 of long-term debt from consolidated VIEs that are included in their respective captions above at June 30, 2021 and December 31, 2020, respectively. For further information, refer to Note 11.

[2] Includes $151 and $161 of residential mortgage loans measured at fair value at June 30, 2021 and December 31, 2020, respectively.