Intangible Assets - Schedule of Intangible Assets (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Finite-Lived Intangible Assets
Gross Carrying Amount	$ 273	$ 298
Accumulated Amortization	(134)	(97)
Net Carrying Amount	139	201
Core deposit intangibles
Finite-Lived Intangible Assets
Gross Carrying Amount	229	229
Accumulated Amortization	(116)	(70)
Net Carrying Amount	113	159
Customer relationships
Finite-Lived Intangible Assets
Gross Carrying Amount	24	29
Accumulated Amortization	(5)	(6)
Net Carrying Amount	19	23
Operating leases
Finite-Lived Intangible Assets
Gross Carrying Amount	17	23
Accumulated Amortization	(12)	(9)
Net Carrying Amount	5	14
Non-compete agreements
Finite-Lived Intangible Assets
Gross Carrying Amount		13
Accumulated Amortization		(11)
Net Carrying Amount		2
Other
Finite-Lived Intangible Assets
Gross Carrying Amount	3	4
Accumulated Amortization	(1)	(1)
Net Carrying Amount	$ 2	$ 3