Fee Income from Contracts with Customers - Disaggregation (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025
Disaggregation of Revenue [Line Items]
Other non-fee revenue	$ 206	$ 200	$ 397	$ 393
Total other revenues	612	518	1,156	1,034
Total Fee Income
Disaggregation of Revenue [Line Items]
Total fee income from contracts with customers	406	318	759	641
Trust and investment management fees
Disaggregation of Revenue [Line Items]
Total fee income from contracts with customers	46	41	94	82
Account services
Disaggregation of Revenue [Line Items]
Total fee income from contracts with customers	84	80	166	159
Credit facilities
Disaggregation of Revenue [Line Items]
Total fee income from contracts with customers	127	71	216	148
Credit card fees, net
Disaggregation of Revenue [Line Items]
Total fee income from contracts with customers	19	17	38	31
Other fees(1)
Disaggregation of Revenue [Line Items]
Total fee income from contracts with customers	11	11	24	20
Other fees(1) \| Previously reported in other income (loss)
Disaggregation of Revenue [Line Items]
Total fee income from contracts with customers			1
Other fees and commissions
Disaggregation of Revenue [Line Items]
Total fee income from contracts with customers	241	179	444	358
Servicing and other fees from HSBC affiliates
Disaggregation of Revenue [Line Items]
Total fee income from contracts with customers	119	98	221	200
Insurance
Disaggregation of Revenue [Line Items]
Total fee income from contracts with customers	$ 0	$ 0	$ 0	$ 1