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, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	$ 5,730	$ 5,928	$ 5,361	$ 2,742
Acquisition PCD reserves	(59)		1,056
Charge-offs	(206)	(247)	(877)	(865)
Recoveries	125	92	344	262
Net (charge-offs)	(81)	(155)	(533)	(603)
Provision for (recapture of) credit losses	(229)	(23)	(525)	3,149
Other	(6)	1	(4)
Ending balance	5,355	5,751	5,355	5,751
Off-Balance Sheet, Credit Loss, Liability [Roll Forward]
Beginning balance	645	662	584	318
Acquisition PCD reserves			46
Provision for (recapture of) credit losses	1	27	16	192
Ending balance	646	689	646	689
Allowance for credit loss	6,001	6,440	6,001	6,440
Allowances for investment securities and other financial assets	162	98	162	98
Total commercial
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	3,812	3,380	3,337	1,812
Acquisition PCD reserves	(54)		774
Charge-offs	(50)	(64)	(393)	(269)
Recoveries	29	26	81	65
Net (charge-offs)	(21)	(38)	(312)	(204)
Provision for (recapture of) credit losses	(129)	185	(193)	2,224
Other	(5)	1	(3)
Ending balance	3,603	3,528	3,603	3,528
Off-Balance Sheet, Credit Loss, Liability [Roll Forward]
Beginning balance	533	548	485	316
Acquisition PCD reserves			43
Provision for (recapture of) credit losses	2	34	7	213
Ending balance	535	582	535	582
Allowance for credit loss	4,138	4,110	4,138	4,110
Total consumer
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	1,918	2,548	2,024	930
Acquisition PCD reserves	(5)		282
Charge-offs	(156)	(183)	(484)	(596)
Recoveries	96	66	263	197
Net (charge-offs)	(60)	(117)	(221)	(399)
Provision for (recapture of) credit losses	(100)	(208)	(332)	925
Other	(1)		(1)
Ending balance	1,752	2,223	1,752	2,223
Off-Balance Sheet, Credit Loss, Liability [Roll Forward]
Beginning balance	112	114	99	2
Acquisition PCD reserves			3
Provision for (recapture of) credit losses	(1)	(7)	9	(21)
Ending balance	111	107	111	107
Allowance for credit loss	1,863	2,330	1,863	2,330
Cumulative Effect, Period of Adoption, Adjustment
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 | 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 | 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	5,730	5,928	5,361	3,205
Off-Balance Sheet, Credit Loss, Liability [Roll Forward]
Beginning balance	645	662	584	497
Cumulative Effect, Period of Adoption, Adjusted Balance | Total commercial
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	3,812	3,380	3,337	1,508
Off-Balance Sheet, Credit Loss, Liability [Roll Forward]
Beginning balance	533	548	485	369
Cumulative Effect, Period of Adoption, Adjusted Balance | Total consumer
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	1,918	2,548	2,024	1,697
Off-Balance Sheet, Credit Loss, Liability [Roll Forward]
Beginning balance	$ 112	$ 114	$ 99	$ 128