Allowance for Credit Losses - Updates to Economic Scenarios (Details) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2020 USD ($)	Jun. 30, 2020 USD ($)	Mar. 31, 2020 scenario	Jan. 01, 2020 USD ($)
Measurement of ECL Measurements [Line Items]
Number of COVID-19 economic scenarios | scenario			3
Increase to management judgment allowance for risk factors associated with large loan exposure in our commercial loan portfolio	$ 27	$ 122
Management judgment allowance for risk factors associated with large loan exposure in our commercial loan portfolio	$ 247	$ 247		$ 125