Fair Value Disclosures - Narrative (Details) $ in Millions	Mar. 31, 2020 USD ($) Multiple	Dec. 31, 2019 USD ($)
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]
LHFS at fair value	$ 3,655	$ 5,673
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 Nonrecurring Basis [Line Items]
LHFS at fair value	41	107
Carrying Amount
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]
LHFS at fair value	728
Level 3
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]
LHFS at fair value	$ 0	$ 0
Private Equity Investments | Minimum | EBITDA Multiple
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]
Unobservable inputs, EBITDA multiples | Multiple	6
Private Equity Investments | Maximum | EBITDA Multiple
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]
Unobservable inputs, EBITDA multiples	14
Private Equity Investments | Weighted average | EBITDA Multiple
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]
Unobservable inputs, EBITDA multiples | Multiple	8
Re-REMIC | Non-agency MBS | Level 3
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]
Difference between fair value of securities held and the fair value of the underlying securities, percentage	38.70%