Intangible Assets - Schedule of Intangible Assets (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Finite-Lived Intangible Assets
Gross Carrying Amount	$ 333	$ 273
Accumulated Amortization	(164)	(134)
Net Carrying Amount	169	139
Core deposit intangibles
Finite-Lived Intangible Assets
Gross Carrying Amount	229	229
Accumulated Amortization	(144)	(116)
Net Carrying Amount	85	113
Developed technology
Finite-Lived Intangible Assets
Gross Carrying Amount	62
Accumulated Amortization	(1)
Net Carrying Amount	61
Customer relationships
Finite-Lived Intangible Assets
Gross Carrying Amount	25	24
Accumulated Amortization	(7)	(5)
Net Carrying Amount	18	19
Operating leases
Finite-Lived Intangible Assets
Gross Carrying Amount	13	17
Accumulated Amortization	(10)	(12)
Net Carrying Amount	3	5
Other
Finite-Lived Intangible Assets
Gross Carrying Amount	4	3
Accumulated Amortization	(2)	(1)
Net Carrying Amount	$ 2	$ 2