Outstanding Loans and Leases - Past Due (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	$ 972,910		$ 972,910		$ 946,895
Percentage of outstandings, total outstanding	100.00%		100.00%		100.00%
Loans and leases, measured at fair value	$ 7,674		$ 7,674		$ 4,349
Loans and leases, pledged as collateral	29,600		29,600		36,700
Loans pledged to secure borrowings	165,100		165,100		166,100
Proceeds from sales of loans			9,757	$ 13,600
Direct/Indirect Consumer | Nonperforming Financing Receivable
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonperforming loans	51		51		53
Residential Mortgage | Federal National Mortgage Association Certificates and Obligations (FNMA) and Federal Home Loan Mortgage Corporation Certificates and Obligations (FHLMC)
Financing Receivable, Recorded Investment, Past Due [Line Items]
Long-term credit protection agreements, amount covered	7,000		7,000		6,100
Estimate of Fair Value Measurement
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	$ 7,674		$ 7,674		$ 4,349
Percentage of outstandings, total outstanding	0.79%		0.79%		0.46%
Consumer Portfolio Segment
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	$ 455,676		$ 455,676		$ 447,231
Consumer Portfolio Segment | Residential Mortgage
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, measured at fair value	275		275		336
Consumer Portfolio Segment | Home equity lines of credit
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases, measured at fair value	365		365		346
Consumer Portfolio Segment | Carrying Value
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	455,036		455,036		446,549
Consumer Portfolio Segment | Estimate of Fair Value Measurement
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	640		640		682
Consumer real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Proceeds from sales of loans	2,300	$ 3,900	4,200	$ 6,500
Consumer real estate | Nonperforming Financing Receivable
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonperforming loans	852		852		1,800
Consumer real estate | Core Portfolio Residential Mortgage
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	216,223		216,223		193,695
Consumer real estate | Core Portfolio Residential Mortgage | Fully Insured Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	16,073		16,073		16,618
Consumer real estate | Core Portfolio Home Equity
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	36,116		36,116		40,010
Consumer real estate | Non-core Residential Mortgage
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	11,249		11,249		14,862
Consumer real estate | Non-core Residential Mortgage | Fully Insured Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	2,618		2,618		3,512
Consumer real estate | Non-core Home Equity
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	5,458		5,458		8,276
Consumer real estate | Carrying Value | Core Portfolio Residential Mortgage
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	216,223		216,223		193,695
Consumer real estate | Carrying Value | Core Portfolio Home Equity
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	36,116		36,116		40,010
Consumer real estate | Carrying Value | Non-core Residential Mortgage
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	11,249		11,249		14,862
Consumer real estate | Carrying Value | Non-core Home Equity
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	5,458		5,458		8,276
Consumer real estate | Estimate of Fair Value Measurement
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	640		640		682
Credit card and other consumer | Credit Card Receivable | United States
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	94,946		94,946		98,338
Credit card and other consumer | Direct/Indirect Consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	90,836		90,836		91,166
Credit card and other consumer | Direct/Indirect Consumer | Dealer Financial Services Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	50,300		50,300		50,100
Credit card and other consumer | Direct/Indirect Consumer | Unsecured Consumer Lending Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	328		328		383
Credit card and other consumer | Direct/Indirect Consumer | Securities Based Lending Loans | United States
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	36,500		36,500		37,000
Credit card and other consumer | Direct/Indirect Consumer | Securities Based Lending Loans | Non United States
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	3,000		3,000		2,900
Credit card and other consumer | Direct/Indirect Consumer | Other Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	694		694		746
Credit card and other consumer | Other consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	208		208		202
Credit card and other consumer | Carrying Value | Credit Card Receivable | United States
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	94,946		94,946		98,338
Credit card and other consumer | Carrying Value | Direct/Indirect Consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	90,836		90,836		91,166
Credit card and other consumer | Carrying Value | Other consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	208		208		202
Commercial Portfolio Segment
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	517,234		517,234		499,664
Commercial Portfolio Segment | United States
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	310,982		310,982		299,277
Loans and leases, measured at fair value	4,700		4,700		2,500
Commercial Portfolio Segment | Non United States
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	101,084		101,084		98,776
Loans and leases, measured at fair value	2,400		2,400		1,100
Commercial Portfolio Segment | Commercial Real Estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	62,798		62,798		60,845
Commercial Portfolio Segment | Commercial Real Estate | United States
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	58,100		58,100		56,600
Commercial Portfolio Segment | Commercial Real Estate | Non United States
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	4,700		4,700		4,200
Commercial Portfolio Segment | Commercial Lease Financing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	20,107		20,107		22,534
Commercial Portfolio Segment | Small Business Commercial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	15,229		15,229		14,565
Commercial Portfolio Segment | Carrying Value
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	510,200		510,200		495,997
Commercial Portfolio Segment | Carrying Value | United States
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	310,982		310,982		299,277
Commercial Portfolio Segment | Carrying Value | Non United States
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	101,084		101,084		98,776
Commercial Portfolio Segment | Carrying Value | Commercial Real Estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	62,798		62,798		60,845
Commercial Portfolio Segment | Carrying Value | Commercial Lease Financing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	20,107		20,107		22,534
Commercial Portfolio Segment | Carrying Value | Small Business Commercial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	15,229		15,229		14,565
Commercial Portfolio Segment | Estimate of Fair Value Measurement
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	7,034		7,034		3,667
30 to 59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	$ 3,567		$ 3,567		$ 4,009
Percentage of outstandings	0.37%		0.37%		0.42%
30 to 59 Days Past Due | Consumer Portfolio Segment
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	$ 2,668		$ 2,668		$ 3,178
30 to 59 Days Past Due | Consumer real estate | Fully Insured Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-performing troubled debt with no change in repayment terms at time of discharge, past due	510		510		637
30 to 59 Days Past Due | Consumer real estate | Nonperforming Financing Receivable
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-performing troubled debt with no change in repayment terms at time of discharge, past due	149		149		217
30 to 59 Days Past Due | Consumer real estate | Core Portfolio Residential Mortgage
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	1,156		1,156		1,188
30 to 59 Days Past Due | Consumer real estate | Core Portfolio Home Equity
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	145		145		200
30 to 59 Days Past Due | Consumer real estate | Non-core Residential Mortgage
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	491		491		757
30 to 59 Days Past Due | Consumer real estate | Non-core Home Equity
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	41		41		139
30 to 59 Days Past Due | Credit card and other consumer | Credit Card Receivable | United States
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	564		564		577
30 to 59 Days Past Due | Credit card and other consumer | Direct/Indirect Consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	271		271		317
30 to 59 Days Past Due | Credit card and other consumer | Other consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	0		0		0
30 to 59 Days Past Due | Commercial Portfolio Segment
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	899		899		831
30 to 59 Days Past Due | Commercial Portfolio Segment | United States
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	589		589		594
30 to 59 Days Past Due | Commercial Portfolio Segment | Non United States
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	60		60		1
30 to 59 Days Past Due | Commercial Portfolio Segment | Commercial Real Estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	135		135		29
30 to 59 Days Past Due | Commercial Portfolio Segment | Commercial Lease Financing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	31		31		124
30 to 59 Days Past Due | Commercial Portfolio Segment | Small Business Commercial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	84		84		83
60 to 89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	$ 1,327		$ 1,327		$ 1,685
Percentage of outstandings	0.14%		0.14%		0.18%
60 to 89 Days Past Due | Consumer Portfolio Segment
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	$ 1,018		$ 1,018		$ 1,220
60 to 89 Days Past Due | Consumer real estate | Fully Insured Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-performing troubled debt with no change in repayment terms at time of discharge, past due	206		206		269
60 to 89 Days Past Due | Consumer real estate | Nonperforming Financing Receivable
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-performing troubled debt with no change in repayment terms at time of discharge, past due	116		116		146
60 to 89 Days Past Due | Consumer real estate | Core Portfolio Residential Mortgage
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	232		232		249
60 to 89 Days Past Due | Consumer real estate | Core Portfolio Home Equity
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	63		63		85
60 to 89 Days Past Due | Consumer real estate | Non-core Residential Mortgage
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	211		211		309
60 to 89 Days Past Due | Consumer real estate | Non-core Home Equity
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	19		19		69
60 to 89 Days Past Due | Credit card and other consumer | Credit Card Receivable | United States
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	413		413		418
60 to 89 Days Past Due | Credit card and other consumer | Direct/Indirect Consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	80		80		90
60 to 89 Days Past Due | Credit card and other consumer | Other consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	0		0		0
60 to 89 Days Past Due | Commercial Portfolio Segment
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	309		309		465
60 to 89 Days Past Due | Commercial Portfolio Segment | United States
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	222		222		232
60 to 89 Days Past Due | Commercial Portfolio Segment | Non United States
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	9		9		49
60 to 89 Days Past Due | Commercial Portfolio Segment | Commercial Real Estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	12		12		16
60 to 89 Days Past Due | Commercial Portfolio Segment | Commercial Lease Financing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	14		14		114
60 to 89 Days Past Due | Commercial Portfolio Segment | Small Business Commercial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	52		52		54
90 Days or More Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	$ 4,142		$ 4,142		$ 5,474
Percentage of outstandings	0.42%		0.42%		0.58%
90 Days or More Past Due | Consumer Portfolio Segment
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	$ 3,336		$ 3,336		$ 4,754
90 Days or More Past Due | Consumer real estate | Fully Insured Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-performing troubled debt with no change in repayment terms at time of discharge, past due	1,200		1,200		1,900
90 Days or More Past Due | Consumer real estate | Core Portfolio Residential Mortgage
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	665		665		793
90 Days or More Past Due | Consumer real estate | Core Portfolio Home Equity
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	202		202		387
90 Days or More Past Due | Consumer real estate | Non-core Residential Mortgage
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	1,390		1,390		2,201
90 Days or More Past Due | Consumer real estate | Non-core Home Equity
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	88		88		339
90 Days or More Past Due | Credit card and other consumer | Credit Card Receivable | United States
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	960		960		994
90 Days or More Past Due | Credit card and other consumer | Direct/Indirect Consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	31		31		40
90 Days or More Past Due | Credit card and other consumer | Other consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	0		0		0
90 Days or More Past Due | Commercial Portfolio Segment
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	806		806		720
90 Days or More Past Due | Commercial Portfolio Segment | United States
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	624		624		573
90 Days or More Past Due | Commercial Portfolio Segment | Non United States
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	10		10		0
90 Days or More Past Due | Commercial Portfolio Segment | Commercial Real Estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	23		23		14
90 Days or More Past Due | Commercial Portfolio Segment | Commercial Lease Financing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	47		47		37
90 Days or More Past Due | Commercial Portfolio Segment | Small Business Commercial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	102		102		96
Total Past Due 30 Days or More
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	$ 9,036		$ 9,036		$ 11,168
Percentage of outstandings	0.93%		0.93%		1.18%
Total Past Due 30 Days or More | Consumer Portfolio Segment
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	$ 7,022		$ 7,022		$ 9,152
Total Past Due 30 Days or More | Consumer real estate | Core Portfolio Residential Mortgage
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	2,053		2,053		2,230
Total Past Due 30 Days or More | Consumer real estate | Core Portfolio Home Equity
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	410		410		672
Total Past Due 30 Days or More | Consumer real estate | Non-core Residential Mortgage
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	2,092		2,092		3,267
Total Past Due 30 Days or More | Consumer real estate | Non-core Home Equity
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	148		148		547
Total Past Due 30 Days or More | Credit card and other consumer | Credit Card Receivable | United States
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	1,937		1,937		1,989
Total Past Due 30 Days or More | Credit card and other consumer | Direct/Indirect Consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	382		382		447
Total Past Due 30 Days or More | Credit card and other consumer | Other consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	0		0		0
Total Past Due 30 Days or More | Commercial Portfolio Segment
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	2,014		2,014		2,016
Total Past Due 30 Days or More | Commercial Portfolio Segment | United States
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	1,435		1,435		1,399
Total Past Due 30 Days or More | Commercial Portfolio Segment | Non United States
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	79		79		50
Total Past Due 30 Days or More | Commercial Portfolio Segment | Commercial Real Estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	170		170		59
Total Past Due 30 Days or More | Commercial Portfolio Segment | Commercial Lease Financing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	92		92		275
Total Past Due 30 Days or More | Commercial Portfolio Segment | Small Business Commercial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	238		238		233
Total Current or Less Than 30 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	$ 956,200		$ 956,200		$ 931,378
Percentage of outstandings, total outstanding	98.28%		98.28%		98.36%
Total Current or Less Than 30 Days Past Due | Consumer Portfolio Segment
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	$ 448,014		$ 448,014		$ 437,397
Total Current or Less Than 30 Days Past Due | Consumer real estate | Core Portfolio Residential Mortgage
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	214,170		214,170		191,465
Total Current or Less Than 30 Days Past Due | Consumer real estate | Core Portfolio Home Equity
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	35,706		35,706		39,338
Total Current or Less Than 30 Days Past Due | Consumer real estate | Non-core Residential Mortgage
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	9,157		9,157		11,595
Total Current or Less Than 30 Days Past Due | Consumer real estate | Non-core Home Equity
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	5,310		5,310		7,729
Total Current or Less Than 30 Days Past Due | Credit card and other consumer | Credit Card Receivable | United States
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	93,009		93,009		96,349
Total Current or Less Than 30 Days Past Due | Credit card and other consumer | Direct/Indirect Consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	90,454		90,454		90,719
Total Current or Less Than 30 Days Past Due | Credit card and other consumer | Other consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	208		208		202
Total Current or Less Than 30 Days Past Due | Commercial Portfolio Segment
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	508,186		508,186		493,981
Total Current or Less Than 30 Days Past Due | Commercial Portfolio Segment | United States
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	309,547		309,547		297,878
Total Current or Less Than 30 Days Past Due | Commercial Portfolio Segment | Non United States
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	101,005		101,005		98,726
Total Current or Less Than 30 Days Past Due | Commercial Portfolio Segment | Commercial Real Estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	62,628		62,628		60,786
Total Current or Less Than 30 Days Past Due | Commercial Portfolio Segment | Commercial Lease Financing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	20,015		20,015		22,259
Total Current or Less Than 30 Days Past Due | Commercial Portfolio Segment | Small Business Commercial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and leases	$ 14,991		$ 14,991		$ 14,332