Fair Value Measurements (Assets And Liabilities Recorded At Fair Value On A Nonrecurring Basis) (Details) - Nonrecurring - Level 3 - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Assets and Liabilities Measured at Fair Value on a Nonrecurring Basis [Line Items]
Loans		$ 282
Other real estate		1
Total assets at fair value	$ 116	283
Commercial borrower | Domestic loans
Assets and Liabilities Measured at Fair Value on a Nonrecurring Basis [Line Items]
Loans	111	256
Commercial borrower | International loans
Assets and Liabilities Measured at Fair Value on a Nonrecurring Basis [Line Items]
Loans		11
Commercial borrower | Commercial mortgage loans | Domestic loans
Assets and Liabilities Measured at Fair Value on a Nonrecurring Basis [Line Items]
Loans	$ 5	$ 15