Intangible Assets - Finite-Lived Intangible Assets (Details) - USD ($) $ in Millions	Mar. 31, 2025	Dec. 31, 2024
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 726	$ 726
Accumulated Amortization	(267)	(238)
Net Carrying Value	459	488
Core deposit intangible
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	700	700
Accumulated Amortization	(256)	(229)
Net Carrying Value	444	471
Other intangible assets
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	26	26
Accumulated Amortization	(11)	(9)
Net Carrying Value	$ 15	$ 17