Commitments, Contingent Liabilities and Guarantees - Standby and Commercial Letters of Credit, Conditional Commitments Issued to Guarantee the Performance of a Customer to a Third Party (Details) - Letters of credit $ in Millions	Mar. 31, 2021 USD ($)
Line of Credit Facility
Commitments	$ 1,869
Less than 1 year
Line of Credit Facility
Commitments	1,016
Less than 1 year | Commercial
Line of Credit Facility
Commitments	10
1 - 5 years
Line of Credit Facility
Commitments	851
1 - 5 years | Commercial
Line of Credit Facility
Commitments	2
Over 5 years
Line of Credit Facility
Commitments	$ 2