Loans and Related Allowance for Credit Losses (Rollforward of Allowance for Credit Losses of Loans and Leases) (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	$ 2,742	$ 2,629
Charge-offs	(618)	(442)
Recoveries	170	164
Net (charge-offs)	(448)	(278)
Provision for credit losses	3,172	369
Other	(1)
Ending balance	5,928	2,721
Off-Balance Sheet, Credit Loss, Liability [Roll Forward]
Beginning balance	318
Provision for (recapture of) credit losses	165
Ending balance	662
Allowance for credit loss	6,590
Total commercial
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	1,812	1,663
Charge-offs	(205)	(84)
Recoveries	39	40
Net (charge-offs)	(166)	(44)
Provision for credit losses	2,039	187
Other	(1)
Ending balance	3,380	1,799
Off-Balance Sheet, Credit Loss, Liability [Roll Forward]
Beginning balance	316
Provision for (recapture of) credit losses	179
Ending balance	548
Allowance for credit loss	3,928
Total consumer
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	930	966
Charge-offs	(413)	(358)
Recoveries	131	124
Net (charge-offs)	(282)	(234)
Provision for credit losses	1,133	182
Ending balance	2,548	$ 922
Off-Balance Sheet, Credit Loss, Liability [Roll Forward]
Beginning balance	2
Provision for (recapture of) credit losses	(14)
Ending balance	114
Allowance for credit loss	2,662
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	3,205
Off-Balance Sheet, Credit Loss, Liability [Roll Forward]
Beginning balance	497
Allowance for credit loss	6,590		$ 3,702
Cumulative Effect, Period of Adoption, Adjusted Balance | Total commercial
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	1,508
Off-Balance Sheet, Credit Loss, Liability [Roll Forward]
Beginning balance	369
Cumulative Effect, Period of Adoption, Adjusted Balance | Total consumer
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	1,697
Off-Balance Sheet, Credit Loss, Liability [Roll Forward]
Beginning balance	$ 128