Allowance for Credit Losses - Updates to Economic Scenarios for Impact of Covid-19 (Details) $ in Millions	Mar. 31, 2020 USD ($) quarter scenario Year	Jan. 01, 2020 USD ($)
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	$ 95
Management judgment allowance for risk factors associated with large loan exposure in our commercial loan portfolio	220	$ 125
Increase to management judgment allowance for recent economic events and deteriorating conditions in our consumer loan portfolio	$ 41
Forecast Period 2020 [Member] | Mild Scenario [Member]
Measurement of ECL Measurements [Line Items]
Number of quarters of economic contraction for GDP | quarter	1
Forecast Period 2020 [Member] | Moderate Scenario [Member]
Measurement of ECL Measurements [Line Items]
Equity price decline (exceeds percent for all periods)	20.00%
Forecast Period 2020 [Member] | Severe Scenario [Member]
Measurement of ECL Measurements [Line Items]
Equity price decline (exceeds percent for all periods)	40.00%
Forecast Period through late 2021 [Member] | Severe Scenario [Member]
Measurement of ECL Measurements [Line Items]
Housing price decrease (exceeds percent)	20.00%
Forecast Period beginning in the second quarter of 2020 [Member] | Severe Scenario [Member]
Measurement of ECL Measurements [Line Items]
10-year U.S. Treasury bond yields (below percent)	(1.00%)
Minimum [Member] | Mild Scenario [Member]
Measurement of ECL Measurements [Line Items]
Period of moderate worsening for unemployment and housing prices | Year	1
Maximum [Member] | Mild Scenario [Member]
Measurement of ECL Measurements [Line Items]
Period of moderate worsening for unemployment and housing prices | Year	2