Intangible Assets - Schedule of Intangible Assets (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Finite-Lived Intangible Assets
Gross Carrying Amount	$ 284	$ 298
Accumulated Amortization	(127)	(97)
Net Carrying Amount	157	201
Core deposit intangibles
Finite-Lived Intangible Assets
Gross Carrying Amount	229	229
Accumulated Amortization	(104)	(70)
Net Carrying Amount	125	159
Customer relationships
Finite-Lived Intangible Assets
Gross Carrying Amount	29	29
Accumulated Amortization	(7)	(6)
Net Carrying Amount	22	23
Operating leases
Finite-Lived Intangible Assets
Gross Carrying Amount	19	23
Accumulated Amortization	(13)	(9)
Net Carrying Amount	6	14
Non-compete agreements
Finite-Lived Intangible Assets
Gross Carrying Amount	3	13
Accumulated Amortization	(2)	(11)
Net Carrying Amount	1	2
Other
Finite-Lived Intangible Assets
Gross Carrying Amount	4	4
Accumulated Amortization	(1)	(1)
Net Carrying Amount	$ 3	$ 3