Loans and Related Allowance for Credit Losses (Rollforward of Allowance for Credit Losses of Loans and Leases) (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	$ 5,928	$ 2,742	$ 2,629
Charge-offs	(247)	(865)	(683)
Recoveries	92	262	250
Net (charge-offs)	(155)	(603)	(433)
Provision for (recapture of) credit losses	(23)	3,149	552
Other	1
Ending balance	5,751	5,751	2,738
Off-Balance Sheet, Credit Loss, Liability [Roll Forward]
Beginning balance	662	318
Provision for (recapture of) credit losses	27	192
Ending balance	689	689
Allowance for credit loss	6,440	6,440
Allowances for investment securities and other financial assets	98	98
Total commercial
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	3,380	1,812	1,663
Charge-offs	(64)	(269)	(138)
Recoveries	26	65	59
Net (charge-offs)	(38)	(204)	(79)
Provision for (recapture of) credit losses	185	2,224	247
Other	1
Ending balance	3,528	3,528	1,811
Off-Balance Sheet, Credit Loss, Liability [Roll Forward]
Beginning balance	548	316
Provision for (recapture of) credit losses	34	213
Ending balance	582	582
Allowance for credit loss	4,110	4,110
Total consumer
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	2,548	930	966
Charge-offs	(183)	(596)	(545)
Recoveries	66	197	191
Net (charge-offs)	(117)	(399)	(354)
Provision for (recapture of) credit losses	(208)	925	305
Ending balance	2,223	2,223	$ 927
Off-Balance Sheet, Credit Loss, Liability [Roll Forward]
Beginning balance	114	2
Provision for (recapture of) credit losses	(7)	(21)
Ending balance	107	107
Allowance for credit loss	2,330	2,330
Cumulative Effect, Period of Adoption, Adjustment | Accounting Standards Update 2016-13
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance		463
Off-Balance Sheet, Credit Loss, Liability [Roll Forward]
Beginning balance		179
Cumulative Effect, Period of Adoption, Adjustment | Accounting Standards Update 2016-13 | Total commercial
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance		(304)
Off-Balance Sheet, Credit Loss, Liability [Roll Forward]
Beginning balance		53
Cumulative Effect, Period of Adoption, Adjustment | Accounting Standards Update 2016-13 | Total consumer
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance		767
Off-Balance Sheet, Credit Loss, Liability [Roll Forward]
Beginning balance		126
Cumulative Effect, Period of Adoption, Adjusted Balance
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	5,928	3,205
Off-Balance Sheet, Credit Loss, Liability [Roll Forward]
Beginning balance	662	497
Allowance for credit loss	6,440	6,440		$ 3,702
Cumulative Effect, Period of Adoption, Adjusted Balance | Total commercial
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	3,380	1,508
Off-Balance Sheet, Credit Loss, Liability [Roll Forward]
Beginning balance	548	369
Cumulative Effect, Period of Adoption, Adjusted Balance | Total consumer
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	2,548	1,697
Off-Balance Sheet, Credit Loss, Liability [Roll Forward]
Beginning balance	$ 114	$ 128