Guarantees and Commitments (Schedule of Guarantor Obligations) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Guarantor Obligations [Line Items]
Letters of Credit Outstanding, Amount	$ 4	$ 6
Cash collateral received for standby letters of credit	0
Maximum
Guarantor Obligations [Line Items]
Letters of Credit Outstanding, Amount	$ 262	$ 249