Fair Value Disclosures - Narrative (Details) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]
Investments excluded from Fair Value Hierarchy, net asset value practical expedient	$ 276
LHFS at fair value	5,515	$ 5,673
Carrying value of unfunded commitments	431	373
Trading assets at fair value	3,824	5,733
Nonperforming
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]
LHFS at fair value	102	107
Carrying Amount
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]
LHFS at fair value	392
Level 3
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]
LHFS at fair value	$ 0	$ 0