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		Sep. 30, 2020		Jun. 30, 2020	Jan. 01, 2020	Dec. 31, 2019		Sep. 30, 2019	Jun. 30, 2019	Dec. 31, 2018
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually evaluated		$ 302				$ 170
Collectively evaluated		2,272				911
Unallocated						121
Total ALLL		2,574	[1]	$ 2,696	$ 33	1,202	[1]	$ 1,143	$ 1,115	$ 1,103
Individually evaluated		2,041				1,529
Collectively evaluated		108,023				107,295
Purchased credit deteriorated		493				551
Total portfolio loans and leases		110,557				109,375
Leveraged leases		366				429
Loans	[1],[2]	110,731				109,558
Residential mortgage loans
Financing Receivable, Allowance for Credit Loss [Line Items]
Residential mortgage loans		174				183
Commercial Leveraged Leases
Financing Receivable, Allowance for Credit Loss [Line Items]
Total ALLL		3				1
Leveraged leases		366				429
Commercial
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually evaluated		178				82
Collectively evaluated		1,355				628
Unallocated						0
Total ALLL		1,533		1,502		710		671	651	645
Individually evaluated		1,111				413
Collectively evaluated		69,743				69,047
Purchased credit deteriorated		396				498
Total portfolio loans and leases		71,250				69,958
Loans		71,250				69,958
Residential Mortgage
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually evaluated		78				55
Collectively evaluated		219				18
Unallocated						0
Total ALLL		297		327		73		75	76	81
Individually evaluated		650				814
Collectively evaluated		15,255				15,690
Purchased credit deteriorated		79				37
Total portfolio loans and leases		15,984				16,541
Residential mortgage loans		174				183
Residential Mortgage | Residential mortgage loans
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans		15,984
Consumer
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually evaluated		46				33
Collectively evaluated		698				265
Unallocated						0
Total ALLL		744		867		298		283	276	267
Individually evaluated		280				302
Collectively evaluated		23,025				22,558
Purchased credit deteriorated		18				16
Total portfolio loans and leases		23,323				22,876
Loans		39,481				39,600
Consumer | Residential mortgage loans | GNMA loans
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans		51
Unallocated
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually evaluated						0
Collectively evaluated						0
Unallocated						121
Total ALLL		$ 0		$ 0		121		$ 114	$ 112	$ 110
Individually evaluated						0
Collectively evaluated						0
Purchased credit deteriorated						0
Total portfolio loans and leases						$ 0

[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.

[2] Includes $174 and $183 of residential mortgage loans measured at fair value at September 30, 2020 and December 31, 2019, respectively.