Fair Value Disclosures - Measured on a Nonrecurring Basis (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	$ 3,310	$ 1,015
Carrying value	8,373	988
Unfunded Commitments Deferred Non Yield Related Loan Fees And Standby Letters Of Credit Carrying Value	373	119
LHFS | Nonrecurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	2,700	0
Valuation Adjustments	(17)	0
Impaired loans | Nonrecurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	95	167
Valuation Adjustments	(23)	(35)
Foreclosed real estate | Nonrecurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	82	35
Valuation Adjustments	$ (248)	$ (240)