Fair Value Measurements (Assets And Liabilities Recorded At Fair Value On A Nonrecurring Basis) (Details) - Nonrecurring - Level 3 - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Assets and Liabilities Measured at Fair Value on a Nonrecurring Basis [Line Items]
Loans		$ 100
Total assets at fair value	$ 70	108
Commercial borrower | Domestic loans
Assets and Liabilities Measured at Fair Value on a Nonrecurring Basis [Line Items]
Loans	$ 70	96
Commercial borrower | Commercial mortgage loans | Domestic loans
Assets and Liabilities Measured at Fair Value on a Nonrecurring Basis [Line Items]
Loans		4
Residential mortgage | Domestic loans
Assets and Liabilities Measured at Fair Value on a Nonrecurring Basis [Line Items]
Loans		$ 8