Investment securities - Fair Value of Investments with Continuous Unrealized Loss Position (Details) - USD ($) $ in Millions	Jun. 30, 2026	Dec. 31, 2025
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract]
Less than 12 months, Fair value	$ 40,980	$ 12,362
Less than 12 months, Unrealized losses	335	55
12 months or more, Fair value	22,673	19,307
12 months or more, Unrealized losses	714	768
Total, Fair value	63,653	31,669
Total, Unrealized losses	1,049	823
U.S. Treasury
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract]
Less than 12 months, Fair value	10,801	378
Less than 12 months, Unrealized losses	62	1
12 months or more, Fair value	7,879	1,671
12 months or more, Unrealized losses	68	24
Total, Fair value	18,680	2,049
Total, Unrealized losses	130	25
Agency residential mortgage-backed securities (“RMBS”)
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract]
Less than 12 months, Fair value	11,024	3,614
Less than 12 months, Unrealized losses	156	26
12 months or more, Fair value	5,100	5,818
12 months or more, Unrealized losses	213	217
Total, Fair value	16,124	9,432
Total, Unrealized losses	369	243
Non-U.S. government
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract]
Less than 12 months, Fair value	12,690	4,120
Less than 12 months, Unrealized losses	75	17
12 months or more, Fair value	2,576	3,195
12 months or more, Unrealized losses	85	130
Total, Fair value	15,266	7,315
Total, Unrealized losses	160	147
Agency commercial mortgage-backed securities (“MBS”)
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract]
Less than 12 months, Fair value	1,256	420
Less than 12 months, Unrealized losses	14	1
12 months or more, Fair value	3,907	4,303
12 months or more, Unrealized losses	107	122
Total, Fair value	5,163	4,723
Total, Unrealized losses	121	123
Foreign covered bonds
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract]
Less than 12 months, Fair value	2,376	1,191
Less than 12 months, Unrealized losses	22	5
12 months or more, Fair value	301	1,338
12 months or more, Unrealized losses	17	52
Total, Fair value	2,677	2,529
Total, Unrealized losses	39	57
Collateralized loan obligations (“CLOs”)
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract]
Less than 12 months, Fair value	1,950	2,280
Less than 12 months, Unrealized losses	2	3
12 months or more, Fair value	104	0
12 months or more, Unrealized losses	0	0
Total, Fair value	2,054	2,280
Total, Unrealized losses	2	3
Non-agency commercial MBS
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract]
Less than 12 months, Fair value	79	78
Less than 12 months, Unrealized losses	0	0
12 months or more, Fair value	1,705	1,881
12 months or more, Unrealized losses	83	85
Total, Fair value	1,784	1,959
Total, Unrealized losses	83	85
Non-agency RMBS
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract]
Less than 12 months, Fair value	397	267
Less than 12 months, Unrealized losses	1	2
12 months or more, Fair value	799	807
12 months or more, Unrealized losses	120	116
Total, Fair value	1,196	1,074
Total, Unrealized losses	121	118
U.S. government agencies
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract]
Less than 12 months, Fair value	392
Less than 12 months, Unrealized losses	3
12 months or more, Fair value	53
12 months or more, Unrealized losses	0
Total, Fair value	445
Total, Unrealized losses	3
Other asset-backed securities (“ABS”)
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract]
Less than 12 months, Fair value	15	14
Less than 12 months, Unrealized losses	0	0
12 months or more, Fair value	249	294
12 months or more, Unrealized losses	21	22
Total, Fair value	264	308
Total, Unrealized losses	$ 21	$ 22

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for more than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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