Intangible Assets (Intangible Assets) (Detail) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Finite-Lived Intangible Assets
Gross Carrying Amount	$ 298	$ 87
Accumulated Amortization	(97)	(47)
Net Carrying Amount	201	40
Core deposit intangibles
Finite-Lived Intangible Assets
Gross Carrying Amount	229	34
Accumulated Amortization	(70)	(30)
Net Carrying Amount	159	4
Customer Relationships
Finite-Lived Intangible Assets
Gross Carrying Amount	29	32
Accumulated Amortization	(6)	(3)
Net Carrying Amount	23	29
Noncompete Agreements
Finite-Lived Intangible Assets
Gross Carrying Amount	13	14
Accumulated Amortization	(11)	(11)
Net Carrying Amount	2	3
Other Intangible Assets
Finite-Lived Intangible Assets
Gross Carrying Amount	4	7
Accumulated Amortization	(1)	(3)
Net Carrying Amount	3	$ 4
Operating lease intangibles
Finite-Lived Intangible Assets
Gross Carrying Amount	23
Accumulated Amortization	(9)
Net Carrying Amount	$ 14