Fair Value Disclosures - Measured on a Nonrecurring Basis (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
LHFS at fair value	$ 3,655		$ 5,673
Carrying Value	5,129		3,310
Carrying value	4,810		8,373
Unfunded Commitments Deferred Non Yield Related Loan Fees And Standby Letters Of Credit Carrying Value	400		373
Nonperforming
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
LHFS at fair value	41		107
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
LHFS at fair value	0		$ 0
LHFS | Nonrecurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
LHFS at fair value	427	$ 0
Valuation Adjustments	(25)	0
Loans and leases | Nonrecurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	101	154
Valuation Adjustments	(7)	(18)
Foreclosed real estate | Nonrecurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	63	33
Valuation Adjustments	$ (73)	$ (63)