Loans (Rollforward of Allowance for Credit Losses of Loans and Leases) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	$ 2,742	$ 2,629
Charge-offs	(304)	(215)
Recoveries	92	79
Net (charge-offs)	(212)	(136)
Provision for credit losses	952	189
Other	(1)
Ending balance	$ 3,944	2,692
Portfolio segment ACL as a percentage of total ACL for loans and leases	100.00%
Ratio of ACL for loans and leases to total loans	1.49%
Provision for (recapture of ) credit losses	$ (47)
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Provision for credit losses	9
Loan Lending Commitment Arrangement Fees
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Provision for (recapture of ) credit losses	47
Other Expense
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Provision for credit losses	952
Total commercial lending
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	1,812	1,663
Charge-offs	(83)	(31)
Recoveries	24	19
Net (charge-offs)	(59)	(12)
Provision for credit losses	531	80
Other	(1)
Ending balance	$ 1,979	1,736
Portfolio segment ACL as a percentage of total ACL for loans and leases	50.00%
Ratio of ACL for loans and leases to total loans	1.07%
Provision for (recapture of ) credit losses	$ (25)
Total consumer lending
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	930	966
Charge-offs	(221)	(184)
Recoveries	68	60
Net (charge-offs)	(153)	(124)
Provision for credit losses	421	109
Ending balance	$ 1,965	$ 956
Portfolio segment ACL as a percentage of total ACL for loans and leases	50.00%
Ratio of ACL for loans and leases to total loans	2.46%
Provision for (recapture of ) credit losses	$ (22)