Off-balance Sheet Lending-related Financial Instruments, Guarantees, and Other Commitments (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Total lending-related commitments	$ 1,048,674	$ 991,482	$ 999,817
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring in 1 year or less	720,969
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring after 1 year through 3 years	141,283
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring after 3 years through 5 years	155,558
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring after 5 years	30,864
Off-balance sheet lending-related financial commitments, Carrying value	1,511	1,512
Maximum
Off balance sheet lending related financial instruments guarantees and other commitments - supplemental information [Abstract]
Secured clearance advance facility maximum outstanding commitment		1,500
Wholesale
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Total lending-related commitments	397,316		$ 372,380
Warranty Reserves
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Loan sale and securitization-related indemnifications, Mortgage repurchase liability, Carrying value	89	111
Total Consumer
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Total lending-related commitments	651,358	621,384
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring in 1 year or less	628,637
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring after 1 year through 3 years	3,187
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring after 3 years through 5 years	2,004
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring after 5 years	17,530
Off-balance sheet lending-related financial commitments, Carrying value	33	33
Total consumer, excluding credit card
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Total lending-related commitments	50,630	48,553
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring in 1 year or less	27,909
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring after 1 year through 3 years	3,187
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring after 3 years through 5 years	2,004
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring after 5 years	17,530
Off-balance sheet lending-related financial commitments, Carrying value	33	33
Home equity
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Total lending-related commitments	20,661	20,360
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring in 1 year or less	916
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring after 1 year through 3 years	1,110
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring after 3 years through 5 years	1,693
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring after 5 years	16,942
Off-balance sheet lending-related financial commitments, Carrying value	12	12
Residential mortgage
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Total lending-related commitments	6,967	5,736
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring in 1 year or less	6,955
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring after 1 year through 3 years	0
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring after 3 years through 5 years	0
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring after 5 years	12
Off-balance sheet lending-related financial commitments, Carrying value	0	0
Auto
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Total lending-related commitments	9,630	9,255
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring in 1 year or less	7,911
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring after 1 year through 3 years	1,430
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring after 3 years through 5 years	200
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring after 5 years	89
Off-balance sheet lending-related financial commitments, Carrying value	2	2
Consumer & Business Banking
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Total lending-related commitments	13,372	13,202
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring in 1 year or less	12,127
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring after 1 year through 3 years	647
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring after 3 years through 5 years	111
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring after 5 years	487
Off-balance sheet lending-related financial commitments, Carrying value	19	19
Credit card
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Total lending-related commitments	600,728	572,831
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring in 1 year or less	600,728
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring after 1 year through 3 years	0
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring after 3 years through 5 years	0
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring after 5 years	0
Off-balance sheet lending-related financial commitments, Carrying value	0	0
Total wholesale
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Total lending-related commitments	397,316	370,098
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring in 1 year or less	92,332
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring after 1 year through 3 years	138,096
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring after 3 years through 5 years	153,554
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring after 5 years	13,334
Off-balance sheet lending-related financial commitments, Carrying value	$ 1,478	$ 1,479
Total wholesale | Wholesale | U.S.
Off balance sheet lending related financial instruments guarantees and other commitments - supplemental information [Abstract]
Off balance sheet lending related financial commitments, percent	76.00%	76.00%
Other unfunded commitments to extend credit
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Total lending-related commitments	$ 361,985	$ 331,160
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring in 1 year or less	74,427
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring after 1 year through 3 years	128,149
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring after 3 years through 5 years	148,414
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring after 5 years	10,995
Off-balance sheet lending-related financial commitments, Carrying value	886	840
Off balance sheet lending related financial instruments guarantees and other commitments - supplemental information [Abstract]
Risk participations for other unfunded commitments to extend credit	287	334
Standby letters of credit and other financial guarantees
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Total lending-related commitments	31,748	35,226
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring in 1 year or less	14,561
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring after 1 year through 3 years	9,810
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring after 3 years through 5 years	5,038
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring after 5 years	2,339
Off-balance sheet lending-related financial commitments, Carrying value	585	636
Other guarantees and commitments, Carrying value	414	444
Loan sale and securitization-related indemnifications, Mortgage repurchase liability, Carrying value	171	192
Off balance sheet lending related financial instruments guarantees and other commitments - supplemental information [Abstract]
Risk participations for standby letters of credit and other financial guarantees	9,900	10,400
Other letters of credit
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Total lending-related commitments	3,583	3,712
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring in 1 year or less	3,344
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring after 1 year through 3 years	137
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring after 3 years through 5 years	102
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring after 5 years	0
Off-balance sheet lending-related financial commitments, Carrying value	7	3
Other guarantees and commitments, Carrying value	0	0
Loan sale and securitization-related indemnifications, Mortgage repurchase liability, Carrying value	7	3
Off balance sheet lending related financial instruments guarantees and other commitments - supplemental information [Abstract]
Risk participations for other letters of credit	469	405
Securities lending indemnification agreements and guarantees
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Other guarantees and commitments, Contractual amount	202,622	179,490
Other guarantees and commitments, Contractual amount, Expiring in 1 year or less	202,622
Other guarantees and commitments, Contractual amount, Expiring after 1 year through 3 years	0
Other guarantees and commitments, Contractual amount, Expiring after 3 years through 5 years	0
Other guarantees and commitments, Contractual amount, Expiring after 5 years	0
Other guarantees and commitments, Carrying value	0	0
Off balance sheet lending related financial instruments guarantees and other commitments - supplemental information [Abstract]
Indemnification agreement securities lending guarantees collateral held in support of	214,300	188,700
Derivatives qualifying as guarantees
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Other guarantees and commitments, Contractual amount	55,894	57,174
Other guarantees and commitments, Contractual amount, Expiring in 1 year or less	2,800
Other guarantees and commitments, Contractual amount, Expiring after 1 year through 3 years	361
Other guarantees and commitments, Contractual amount, Expiring after 3 years through 5 years	12,384
Other guarantees and commitments, Contractual amount, Expiring after 5 years	40,349
Other guarantees and commitments, Carrying value	370	304
Unsettled reverse repurchase and securities borrowing agreements
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Other guarantees and commitments, Contractual amount	119,762	76,859
Other guarantees and commitments, Contractual amount, Expiring in 1 year or less	119,762
Other guarantees and commitments, Contractual amount, Expiring after 1 year through 3 years	0
Other guarantees and commitments, Contractual amount, Expiring after 3 years through 5 years	0
Other guarantees and commitments, Contractual amount, Expiring after 5 years	0
Other guarantees and commitments, Carrying value	0	0
Unsettled repurchase and securities lending agreements
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Other guarantees and commitments, Contractual amount	92,115	44,205
Other guarantees and commitments, Contractual amount, Expiring in 1 year or less	92,115
Other guarantees and commitments, Carrying value	0	0
Loans sold with recourse
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Loan sale and securitization-related indemnifications, Loans sold with recourse, Contractual amount	1,066	1,169
Loan sale and securitization-related indemnifications, Loans sold with recourse, Carrying value	33	38
Other guarantees and commitments
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Other guarantees and commitments, Contractual amount	14,559	11,867
Other guarantees and commitments, Contractual amount, Expiring in 1 year or less	10,091
Other guarantees and commitments, Contractual amount, Expiring after 1 year through 3 years	1,443
Other guarantees and commitments, Contractual amount, Expiring after 3 years through 5 years	384
Other guarantees and commitments, Contractual amount, Expiring after 5 years	2,641
Other guarantees and commitments, Carrying Value	$ (53)	$ (76)
Days Past Due, 60 or More | Credit card
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Line of credit close criteria, period past due	60 days