Fair Value Measurements - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Assets:
Available-for-sale debt and other securities:	$ 40,396		$ 40,396		$ 50,419
Equity securities	428		428		613
Derivative assets	2,098		2,098		2,677
Liabilities:
Derivative liabilities	2,427		2,427		2,999
Pretax unrealized losses	1,909	$ (2,187)	1,359	$ (2,260)
Available-for-sale debt securities transferred to held-to-maturity securities
Liabilities:
Pretax unrealized losses	33		(897)
Residential Mortgage
Assets:
Residential mortgage loans	114	113	114	113	116
U.S. Treasury and federal agencies securities
Assets:
Available-for-sale debt and other securities:	4,350		4,350		4,336
Obligations of states and political subdivisions securities
Assets:
Available-for-sale debt and other securities:	0		0		2
Asset-backed securities and other debt securities
Assets:
Available-for-sale debt and other securities:	4,134		4,134		4,912
Other securities
Assets:
Available-for-sale debt and other securities:	777		777		722
Liabilities:
FHLB, restricted stock holdings	275		275		224
FRB, restricted stock holdings	499		499		496
DTCC, restricted stock holdings	3		3		2
Level 3 | Interest rate contracts
Assets:
Derivative assets	7	5	7	5
Liabilities:
Derivative liabilities	5	$ 7	5	$ 7
Recurring
Assets:
Available-for-sale debt and other securities:	39,619		39,619		49,697
Trading debt securities	1,176		1,176		899
Equity securities	428		428		613
Residential mortgage loans held for sale	512		512		334
Derivative assets	2,098		2,098		2,677
Total assets	45,603		45,603		56,073
Liabilities:
Derivative liabilities	2,427		2,427		2,999
Short positions	231		231		107
Total liabilities	2,658		2,658		3,106
Recurring | Interest rate contracts
Assets:
Derivative assets	647		647		983
Liabilities:
Derivative liabilities	819		819		1,213
Recurring | Foreign exchange contracts
Assets:
Derivative assets	739		739		643
Liabilities:
Derivative liabilities	710		710		600
Recurring | Equity contracts
Liabilities:
Derivative liabilities	196		196		168
Recurring | Commodity contracts
Assets:
Derivative assets	712		712		1,051
Liabilities:
Derivative liabilities	702		702		1,018
Recurring | Servicing rights
Assets:
Servicing rights	1,656		1,656		1,737
Recurring | Residential Mortgage
Assets:
Residential mortgage loans	114		114		116
Recurring | U.S. Treasury and federal agencies securities
Assets:
Available-for-sale debt and other securities:	4,350		4,350		4,336
Trading debt securities	619		619		647
Liabilities:
Short positions	82		82		31
Recurring | Obligations of states and political subdivisions securities
Assets:
Available-for-sale debt and other securities:	0		0		2
Trading debt securities	86		86		39
Recurring | Agency mortgage-backed securities | Residential Mortgage
Assets:
Available-for-sale debt and other securities:	5,017		5,017		10,282
Trading debt securities	12		12		6
Recurring | Agency mortgage-backed securities | Commercial
Assets:
Available-for-sale debt and other securities:	21,719		21,719		25,720
Recurring | Non-agency mortgage-backed securities | Commercial
Assets:
Available-for-sale debt and other securities:	4,399		4,399		4,445
Recurring | Asset-backed securities and other debt securities
Assets:
Available-for-sale debt and other securities:	4,134		4,134		4,912
Trading debt securities	459		459		207
Liabilities:
Short positions	149		149		76
Recurring | Level 1
Assets:
Available-for-sale debt and other securities:	4,350		4,350		4,336
Trading debt securities	596		596		640
Equity securities	394		394		600
Residential mortgage loans held for sale	0		0		0
Derivative assets	154		154		205
Total assets	5,494		5,494		5,781
Liabilities:
Derivative liabilities	34		34		33
Short positions	81		81		31
Total liabilities	115		115		64
Recurring | Level 1 | Interest rate contracts
Assets:
Derivative assets	2		2		0
Liabilities:
Derivative liabilities	4		4		5
Recurring | Level 1 | Foreign exchange contracts
Assets:
Derivative assets	0		0		0
Liabilities:
Derivative liabilities	0		0		0
Recurring | Level 1 | Equity contracts
Liabilities:
Derivative liabilities	0		0		0
Recurring | Level 1 | Commodity contracts
Assets:
Derivative assets	152		152		205
Liabilities:
Derivative liabilities	30		30		28
Recurring | Level 1 | Servicing rights
Assets:
Servicing rights	0		0		0
Recurring | Level 1 | Residential Mortgage
Assets:
Residential mortgage loans	0		0		0
Recurring | Level 1 | U.S. Treasury and federal agencies securities
Assets:
Available-for-sale debt and other securities:	4,350		4,350		4,336
Trading debt securities	596		596		640
Liabilities:
Short positions	81		81		31
Recurring | Level 1 | Obligations of states and political subdivisions securities
Assets:
Available-for-sale debt and other securities:	0		0		0
Trading debt securities	0		0		0
Recurring | Level 1 | Agency mortgage-backed securities | Residential Mortgage
Assets:
Available-for-sale debt and other securities:	0		0		0
Trading debt securities	0		0		0
Recurring | Level 1 | Agency mortgage-backed securities | Commercial
Assets:
Available-for-sale debt and other securities:	0		0		0
Recurring | Level 1 | Non-agency mortgage-backed securities | Commercial
Assets:
Available-for-sale debt and other securities:	0		0		0
Recurring | Level 1 | Asset-backed securities and other debt securities
Assets:
Available-for-sale debt and other securities:	0		0		0
Trading debt securities	0		0		0
Liabilities:
Short positions	0		0		0
Recurring | Level 2
Assets:
Available-for-sale debt and other securities:	35,269		35,269		45,361
Trading debt securities	580		580		259
Equity securities	34		34		13
Residential mortgage loans held for sale	512		512		334
Derivative assets	1,937		1,937		2,466
Total assets	38,332		38,332		48,433
Liabilities:
Derivative liabilities	2,192		2,192		2,792
Short positions	150		150		76
Total liabilities	2,342		2,342		2,868
Recurring | Level 2 | Interest rate contracts
Assets:
Derivative assets	638		638		977
Liabilities:
Derivative liabilities	810		810		1,202
Recurring | Level 2 | Foreign exchange contracts
Assets:
Derivative assets	739		739		643
Liabilities:
Derivative liabilities	710		710		600
Recurring | Level 2 | Equity contracts
Liabilities:
Derivative liabilities	0		0		0
Recurring | Level 2 | Commodity contracts
Assets:
Derivative assets	560		560		846
Liabilities:
Derivative liabilities	672		672		990
Recurring | Level 2 | Servicing rights
Assets:
Servicing rights	0		0		0
Recurring | Level 2 | Residential Mortgage
Assets:
Residential mortgage loans	0		0		0
Recurring | Level 2 | U.S. Treasury and federal agencies securities
Assets:
Available-for-sale debt and other securities:	0		0		0
Trading debt securities	23		23		7
Liabilities:
Short positions	1		1		0
Recurring | Level 2 | Obligations of states and political subdivisions securities
Assets:
Available-for-sale debt and other securities:	0		0		2
Trading debt securities	86		86		39
Recurring | Level 2 | Agency mortgage-backed securities | Residential Mortgage
Assets:
Available-for-sale debt and other securities:	5,017		5,017		10,282
Trading debt securities	12		12		6
Recurring | Level 2 | Agency mortgage-backed securities | Commercial
Assets:
Available-for-sale debt and other securities:	21,719		21,719		25,720
Recurring | Level 2 | Non-agency mortgage-backed securities | Commercial
Assets:
Available-for-sale debt and other securities:	4,399		4,399		4,445
Recurring | Level 2 | Asset-backed securities and other debt securities
Assets:
Available-for-sale debt and other securities:	4,134		4,134		4,912
Trading debt securities	459		459		207
Liabilities:
Short positions	149		149		76
Recurring | Level 3
Assets:
Available-for-sale debt and other securities:	0		0		0
Trading debt securities	0		0		0
Equity securities	0		0		0
Residential mortgage loans held for sale	0		0		0
Derivative assets	7		7		6
Total assets	1,777		1,777		1,859
Liabilities:
Derivative liabilities	201		201		174
Short positions	0		0		0
Total liabilities	201		201		174
Recurring | Level 3 | Interest rate contracts
Assets:
Derivative assets	7		7		6
Liabilities:
Derivative liabilities	5		5		6
Recurring | Level 3 | Foreign exchange contracts
Assets:
Derivative assets	0		0		0
Liabilities:
Derivative liabilities	0		0		0
Recurring | Level 3 | Equity contracts
Liabilities:
Derivative liabilities	196		196		168
Recurring | Level 3 | Commodity contracts
Assets:
Derivative assets	0		0		0
Liabilities:
Derivative liabilities	0		0		0
Recurring | Level 3 | Servicing rights
Assets:
Servicing rights	1,656		1,656		1,737
Recurring | Level 3 | Residential Mortgage
Assets:
Residential mortgage loans	114		114		116
Recurring | Level 3 | U.S. Treasury and federal agencies securities
Assets:
Available-for-sale debt and other securities:	0		0		0
Trading debt securities	0		0		0
Liabilities:
Short positions	0		0		0
Recurring | Level 3 | Obligations of states and political subdivisions securities
Assets:
Available-for-sale debt and other securities:	0		0		0
Trading debt securities	0		0		0
Recurring | Level 3 | Agency mortgage-backed securities | Residential Mortgage
Assets:
Available-for-sale debt and other securities:	0		0		0
Trading debt securities	0		0		0
Recurring | Level 3 | Agency mortgage-backed securities | Commercial
Assets:
Available-for-sale debt and other securities:	0		0		0
Recurring | Level 3 | Non-agency mortgage-backed securities | Commercial
Assets:
Available-for-sale debt and other securities:	0		0		0
Recurring | Level 3 | Asset-backed securities and other debt securities
Assets:
Available-for-sale debt and other securities:	0		0		0
Trading debt securities	0		0		0
Liabilities:
Short positions	$ 0		$ 0		$ 0