Commitments and Contingencies - Off-Balance Sheet Financial Instruments (Details) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Residential Mortgage
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Mortgage loans sold with recourse	$ 373	$ 371
CRE
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Mortgage loans sold with recourse	8,641	8,676
Commitments to extend, originate or purchase credit
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Mortgage loans sold with recourse	175,616	177,598
Letters of credit
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Mortgage loans sold with recourse	$ 5,050	$ 5,181