Off-balance Sheet Lending-related Financial Instruments, Guarantees, and Other Commitments (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Total lending-related commitments	$ 1,045,993	$ 991,482	$ 996,634
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring in 1 year or less	725,776
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring after 1 year through 3 years	142,445
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring after 3 years through 5 years	149,373
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring after 5 years	28,399
Off-balance sheet lending-related financial commitments, Carrying value	1,572	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	401,757		$ 366,498
Warranty Reserves
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Loan sale and securitization-related indemnifications, Mortgage repurchase liability, Carrying value	123	111
Total Consumer
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Total lending-related commitments	644,236	621,384
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring in 1 year or less	622,176
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring after 1 year through 3 years	2,908
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring after 3 years through 5 years	1,856
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring after 5 years	17,296
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	51,784	48,553
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring in 1 year or less	29,724
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring after 1 year through 3 years	2,908
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring after 3 years through 5 years	1,856
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring after 5 years	17,296
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	20,530	20,360
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring in 1 year or less	1,202
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring after 1 year through 3 years	1,163
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring after 3 years through 5 years	1,559
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring after 5 years	16,606
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	8,354	5,736
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring in 1 year or less	8,342
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	9,059	9,255
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring in 1 year or less	7,770
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring after 1 year through 3 years	949
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring after 3 years through 5 years	187
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring after 5 years	153
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	13,841	13,202
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring in 1 year or less	12,410
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring after 1 year through 3 years	796
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring after 3 years through 5 years	110
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring after 5 years	525
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	592,452	572,831
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring in 1 year or less	592,452
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	401,757	370,098
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring in 1 year or less	103,600
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring after 1 year through 3 years	139,537
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring after 3 years through 5 years	147,517
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring after 5 years	11,103
Off-balance sheet lending-related financial commitments, Carrying value	$ 1,539	$ 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	78.00%	77.00%
Other unfunded commitments to extend credit
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Total lending-related commitments	$ 366,678	$ 331,160
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring in 1 year or less	86,217
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring after 1 year through 3 years	130,739
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring after 3 years through 5 years	140,327
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring after 5 years	9,395
Off-balance sheet lending-related financial commitments, Carrying value	942	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	31,963	35,226
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring in 1 year or less	14,469
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring after 1 year through 3 years	8,744
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring after 3 years through 5 years	7,042
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring after 5 years	1,708
Off-balance sheet lending-related financial commitments, Carrying value	593	636
Other guarantees and commitments, Carrying value	454	444
Loan sale and securitization-related indemnifications, Mortgage repurchase liability, Carrying value	139	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	9,800	10,400
Other letters of credit
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Total lending-related commitments	3,116	3,712
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring in 1 year or less	2,914
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring after 1 year through 3 years	54
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring after 3 years through 5 years	148
Off-balance sheet lending-related financial commitments, Contractual amount, Expiring after 5 years
Off-balance sheet lending-related financial commitments, Carrying value	4	3
Other guarantees and commitments, Carrying value	0	0
Loan sale and securitization-related indemnifications, Mortgage repurchase liability, Carrying value	4	3
Off balance sheet lending related financial instruments guarantees and other commitments - supplemental information [Abstract]
Risk participations for other letters of credit	407	405
Securities lending indemnification agreements and guarantees
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Other guarantees and commitments, Contractual amount	202,797	179,490
Other guarantees and commitments, Contractual amount, Expiring in 1 year or less	202,797
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	213,700	188,700
Derivatives qualifying as guarantees
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Other guarantees and commitments, Contractual amount	57,721	57,174
Other guarantees and commitments, Contractual amount, Expiring in 1 year or less	4,737
Other guarantees and commitments, Contractual amount, Expiring after 1 year through 3 years	334
Other guarantees and commitments, Contractual amount, Expiring after 3 years through 5 years	12,415
Other guarantees and commitments, Contractual amount, Expiring after 5 years	40,235
Other guarantees and commitments, Carrying value	457	304
Unsettled reverse repurchase and securities borrowing agreements
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Other guarantees and commitments, Contractual amount	102,480	76,859
Other guarantees and commitments, Contractual amount, Expiring in 1 year or less	102,480
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	92,150	44,205
Other guarantees and commitments, Contractual amount, Expiring in 1 year or less	92,150
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	1,084	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	16,085	11,867
Other guarantees and commitments, Contractual amount, Expiring in 1 year or less	11,754
Other guarantees and commitments, Contractual amount, Expiring after 1 year through 3 years	1,458
Other guarantees and commitments, Contractual amount, Expiring after 3 years through 5 years	209
Other guarantees and commitments, Contractual amount, Expiring after 5 years	2,664
Other guarantees and commitments, Carrying Value	$ (225)	$ (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