Business Segments - Summary on Reconciliation of Results Under IFRS to US GAAP (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025	Dec. 31, 2025
Operating Statistics [Line Items]
Net interest income (expense), U.S. GAAP Consolidated	$ 552	$ 526
Other operating income, U.S. GAAP Consolidated	544	516
Total operating income, U.S. GAAP Consolidated	1,096	1,042
Expected credit losses / provision for credit losses, U.S. GAAP Consolidated	48	118
Total income	1,048	924
Total operating expenses, U.S. GAAP Consolidated	669	660
Income before income tax	379	264
Total assets, U.S. GAAP Consolidated	174,749	172,441	$ 172,410
Total loans, net, U.S. GAAP Consolidated	61,105	62,780	59,452
Goodwill, U.S. GAAP Consolidated	458	458	458
Total deposits, U.S. GAAP Consolidated	121,547	125,724	$ 124,097
Group Reporting Basis Adjustments
Operating Statistics [Line Items]
Net interest income (expense)	5	6
Other operating income	(7)	(3)
Total operating income (expense)	(2)	3
Expected credit losses / provision for credit losses	12	32
Total income	(14)	(29)
Total operating expenses	5	10
Profit (loss) before income tax	(19)	(39)
Total assets	(15,934)	(12,610)
Total loans, net	(86)	(771)
Goodwill	100	100
Total deposits	(2,752)	(2,362)
Group Reporting Basis Reclassifications
Operating Statistics [Line Items]
Net interest income (expense)	6	(39)
Other operating income	7	49
Total operating income (expense)	13	10
Expected credit losses / provision for credit losses	0	0
Total income	13	10
Total operating expenses	13	10
Profit (loss) before income tax	0	0
Total assets	0	0
Total loans, net	1,167	2,411
Goodwill	0	0
Total deposits	6,593	11,393
Operating Segments
Operating Statistics [Line Items]
Net interest income (expense)	541	559
Other operating income	544	470
Total operating income (expense)	1,085	1,029
Expected credit losses / provision for credit losses	36	86
Total income	1,049	943
Direct Costs	198	238
Indirect Costs	453	402
Total operating expenses	651	640
Profit (loss) before income tax	398	303
Total assets	190,683	185,051
Total loans, net	60,024	61,140
Goodwill	358	358
Total deposits	117,706	116,693
IWPB | Operating Segments
Operating Statistics [Line Items]
Net interest income (expense)	190	186
Other operating income	66	51
Total operating income (expense)	256	237
Expected credit losses / provision for credit losses	2	2
Total income	254	235
Direct Costs	84	86
Indirect Costs	102	99
Total operating expenses	186	185
Profit (loss) before income tax	68	50
Total assets	34,529	38,299
Total loans, net	25,690	27,234
Goodwill	0	0
Total deposits	26,726	28,046
CIB | Operating Segments
Operating Statistics [Line Items]
Net interest income (expense)	485	473
Other operating income	347	323
Total operating income (expense)	832	796
Expected credit losses / provision for credit losses	34	84
Total income	798	712
Direct Costs	88	110
Indirect Costs	334	313
Total operating expenses	422	423
Profit (loss) before income tax	376	289
Total assets	152,260	142,336
Total loans, net	34,334	33,906
Goodwill	358	358
Total deposits	90,980	88,647
CC | Operating Segments
Operating Statistics [Line Items]
Net interest income (expense)	(134)	(100)
Other operating income	131	96
Total operating income (expense)	(3)	(4)
Expected credit losses / provision for credit losses	0	0
Total income	(3)	(4)
Direct Costs	26	42
Indirect Costs	17	(10)
Total operating expenses	43	32
Profit (loss) before income tax	(46)	(36)
Total assets	3,894	4,416
Total loans, net	0	0
Goodwill	0	0
Total deposits	$ 0	$ 0