Goodwill and Other Intangible Assets - Schedule of Intangible Assets and Accumulated Amortization Included in the Consolidated Statements of Condition (Details) - USD ($) $ in Millions	Sep. 30, 2025	Dec. 31, 2024
Intangible Assets [Line Items]
Gross Carrying Amount	$ 397	$ 415
Accumulated Amortization	(283)	(272)
Net Carrying Value	114	143
Core deposit intangibles
Intangible Assets [Line Items]
Gross Carrying Amount	354	356
Accumulated Amortization	(256)	(233)
Net Carrying Value	98	123
Client relationships
Intangible Assets [Line Items]
Gross Carrying Amount	32	32
Accumulated Amortization	(20)	(18)
Net Carrying Value	12	14
Other
Intangible Assets [Line Items]
Gross Carrying Amount	11	27
Accumulated Amortization	(7)	(21)
Net Carrying Value	$ 4	$ 6