Loans and Related Allowance for Credit Losses, Allowance Activity by Portfolio Segment (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses for loans, beginning balance	$ 20,436	$ 10,603	$ 10,456
Provision for credit losses, loans	751	695	14,149	$ 2,043
Interest income on certain loans	(41)	(34)	(117)	(112)
Loan charge-offs	(994)	(1,009)	(3,603)	(3,105)
Loan recoveries	311	364	898	1,112
Net loan charge-offs	(683)	(645)	(2,705)	(1,993)
Other	8	(6)	17	(32)
Allowance for credit losses for loans, ending balance	20,471	10,613	20,471	10,613
Purchase credit deteriorated [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses for loans, beginning balance			0
Previous accounting guidance [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses for loans, beginning balance	20,436	10,603	10,456	10,707
Accounting Standards Update 2016-13 [Member] | Cumulative effect from change in accounting policies, period of adoption adjustment [Member] | Not purchased credit deteriorated [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses for loans, beginning balance	0	0	(1,337)	0
Accounting Standards Update 2016-13 [Member] | Cumulative effect from change in accounting policies, period of adoption adjustment [Member] | Purchase credit deteriorated [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses for loans, beginning balance	0	0	8	0
Accounting Standards Update 2016-13 [Member] | Cumulative effect from change in accounting policies, period of adoption adjusted balance [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses for loans, beginning balance	20,436	10,603	9,127	10,707
Total Commercial [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses for loans, beginning balance	11,669	6,298	6,245
Provision for credit losses, loans	241	84	9,480	294
Interest income on certain loans	(18)	(10)	(44)	(35)
Loan charge-offs	(420)	(223)	(1,460)	(654)
Loan recoveries	64	84	178	205
Net loan charge-offs	(356)	(139)	(1,282)	(449)
Other	6	(3)	4	3
Allowance for credit losses for loans, ending balance	11,542	6,230	11,542	6,230
Total Commercial [Member] | Purchase credit deteriorated [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses for loans, beginning balance			0
Total Commercial [Member] | Previous accounting guidance [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses for loans, beginning balance			6,245	6,417
Total Commercial [Member] | Accounting Standards Update 2016-13 [Member] | Cumulative effect from change in accounting policies, period of adoption adjustment [Member] | Not purchased credit deteriorated [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses for loans, beginning balance			(2,861)	0
Total Commercial [Member] | Accounting Standards Update 2016-13 [Member] | Cumulative effect from change in accounting policies, period of adoption adjustment [Member] | Purchase credit deteriorated [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses for loans, beginning balance			0	0
Total Commercial [Member] | Accounting Standards Update 2016-13 [Member] | Cumulative effect from change in accounting policies, period of adoption adjusted balance [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses for loans, beginning balance			3,384	6,417
Total Consumer [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses for loans, beginning balance	8,767	4,305	4,211
Provision for credit losses, loans	510	611	4,669	1,749
Interest income on certain loans	(23)	(24)	(73)	(77)
Loan charge-offs	(574)	(786)	(2,143)	(2,451)
Loan recoveries	247	280	720	907
Net loan charge-offs	(327)	(506)	(1,423)	(1,544)
Other	2	(3)	13	(35)
Allowance for credit losses for loans, ending balance	$ 8,929	$ 4,383	8,929	4,383
Total Consumer [Member] | Purchase credit deteriorated [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses for loans, beginning balance			0
Total Consumer [Member] | Previous accounting guidance [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses for loans, beginning balance			4,211	4,290
Total Consumer [Member] | Accounting Standards Update 2016-13 [Member] | Cumulative effect from change in accounting policies, period of adoption adjustment [Member] | Not purchased credit deteriorated [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses for loans, beginning balance			1,524	0
Total Consumer [Member] | Accounting Standards Update 2016-13 [Member] | Cumulative effect from change in accounting policies, period of adoption adjustment [Member] | Purchase credit deteriorated [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses for loans, beginning balance			8	0
Total Consumer [Member] | Accounting Standards Update 2016-13 [Member] | Cumulative effect from change in accounting policies, period of adoption adjusted balance [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses for loans, beginning balance			$ 5,743	$ 4,290