Business Segments - Summary on Reconciliation of Results Under IFRS to US GAAP (Details) - USD ($) $ in Millions	3 Months Ended			9 Months Ended
	Sep. 30, 2025		Sep. 30, 2024	Sep. 30, 2025		Sep. 30, 2024	Dec. 31, 2024	[1]
Operating Statistics [Line Items]
Net interest income (expense), U.S. GAAP Consolidated	$ 525		$ 439	$ 1,574		$ 1,277
Other operating income, U.S. GAAP Consolidated	548		334	1,582		1,410
Total operating income, U.S. GAAP Consolidated	1,073		773	3,156		2,687
Expected credit losses / provision for credit losses, U.S. GAAP Consolidated	(84)		(13)	76		36
Total income	1,157		786	3,080		2,651
Total operating expenses, U.S. GAAP Consolidated	661		671	2,017		2,040
Income before income tax	496		115	1,063		611
Total assets, U.S. GAAP Consolidated	169,890	[1]	167,799	169,890	[1]	167,799	$ 170,731
Total loans, net, U.S. GAAP Consolidated	63,978	[1]	61,467	63,978	[1]	61,467	62,216
Goodwill, U.S. GAAP Consolidated	458	[1]	458	458	[1]	458	458
Total deposits, U.S. GAAP Consolidated	122,760	[1]	123,373	122,760	[1]	123,373	$ 123,350
Operating Segments
Operating Statistics [Line Items]
Net interest income (expense)	577		451	1,699		1,328
Other operating income	481		313	1,413		1,324
Total operating income	1,058		764	3,112		2,652
Expected credit losses / provision for credit losses	19		19	169		52
Total income	1,039		745	2,943		2,600
Direct Costs	213		228	685		760
Indirect Costs	430		426	1,285		1,237
Total operating expenses	643		654	1,970		1,997
Profit (loss) before income tax	396		91	973		603
Total assets	182,646		181,011	182,646		181,011
Total loans, net	62,615		59,851	62,615		59,851
Goodwill	358		358	358		358
Total deposits	115,618		115,774	115,618		115,774
Group Reporting Basis Adjustments
Operating Statistics [Line Items]
Net interest income (expense)	7		9	19		22
Other operating income	(2)		(7)	(5)		(13)
Total operating income	5		2	14		9
Expected credit losses / provision for credit losses	(103)		(32)	(93)		(16)
Total income	108		34	107		25
Total operating expenses	8		10	17		17
Profit (loss) before income tax	100		24	90		8
Total assets	(12,756)		(13,212)	(12,756)		(13,212)
Total loans, net	(606)		(1,054)	(606)		(1,054)
Goodwill	100		100	100		100
Total deposits	(1,932)		(1,192)	(1,932)		(1,192)
Group Reporting Basis Reclassifications
Operating Statistics [Line Items]
Net interest income (expense)	(59)		(21)	(144)		(73)
Other operating income	69		28	174		99
Total operating income	10		7	30		26
Expected credit losses / provision for credit losses	0		0	0		0
Total income	10		7	30		26
Total operating expenses	10		7	30		26
Profit (loss) before income tax	0		0	0		0
Total assets	0		0	0		0
Total loans, net	1,969		2,670	1,969		2,670
Goodwill	0		0	0		0
Total deposits	9,074		8,791	9,074		8,791
IWPB | Operating Segments
Operating Statistics [Line Items]
Net interest income (expense)	190		175	564		529
Other operating income	66		8	181		133
Total operating income	256		183	745		662
Expected credit losses / provision for credit losses	2		2	5		0
Total income	254		181	740		662
Direct Costs	88		104	280		291
Indirect Costs	110		103	306		301
Total operating expenses	198		207	586		592
Profit (loss) before income tax	56		(26)	154		70
Total assets	38,262		38,385	38,262		38,385
Total loans, net	28,022		25,785	28,022		25,785
Goodwill	0		0	0		0
Total deposits	25,899		28,903	25,899		28,903
CIB | Operating Segments
Operating Statistics [Line Items]
Net interest income (expense)	463		451	1,396		1,301
Other operating income	340		131	976		684
Total operating income	803		582	2,372		1,985
Expected credit losses / provision for credit losses	17		17	164		52
Total income	786		565	2,208		1,933
Direct Costs	100		108	325		317
Indirect Costs	312		315	952		946
Total operating expenses	412		423	1,277		1,263
Profit (loss) before income tax	374		142	931		670
Total assets	139,411		138,348	139,411		138,348
Total loans, net	34,593		34,066	34,593		34,066
Goodwill	358		358	358		358
Total deposits	89,719		86,871	89,719		86,871
CC | Operating Segments
Operating Statistics [Line Items]
Net interest income (expense)	(76)		(175)	(261)		(502)
Other operating income	75		174	256		507
Total operating income	(1)		(1)	(5)		5
Expected credit losses / provision for credit losses	0		0	0		0
Total income	(1)		(1)	(5)		5
Direct Costs	25		16	80		152
Indirect Costs	8		8	27		(10)
Total operating expenses	33		24	107		142
Profit (loss) before income tax	(34)		(25)	(112)		(137)
Total assets	4,973		4,278	4,973		4,278
Total loans, net	0		0	0		0
Goodwill	0		0	0		0
Total deposits	$ 0		$ 0	$ 0		$ 0

[1] The following table summarizes assets and liabilities related to our consolidated variable interest entities ("VIEs") at September 30, 2025 and December 31, 2024. Assets and liabilities exclude intercompany balances that eliminate in consolidation. See Note 15, "Variable Interest Entities," for additional information. September 30, 2025December 31, 2024(in millions)AssetsOther assets$7 $11 Total assets$7 $11 LiabilitiesInterest, taxes and other liabilities$14 $4 Total liabilities$14 $4