v3.20.4
Servicing of Financial Assets (Data And Assumptions Used In The Fair Value Calculation As Well As The Valuation's Sensitivity To Rate Fluctuations Related To Mortgage Servicing Rights) (Details)
$ in Millions
12 Months Ended
Dec. 31, 2020
USD ($)
basis_point
Dec. 31, 2019
USD ($)
basis_point
Dec. 31, 2018
USD ($)
Servicing Assets at Fair Value [Line Items]      
Unpaid principal balance $ 34,454 $ 34,467  
Weighted-average CPR (%) 15.60% 12.00%  
Estimated impact on fair value of a 10% increase $ (23) $ (19)  
Estimated impact on fair value of a 20% increase $ (42) $ (35)  
Option-adjusted spread (basis points) | basis_point 560 618  
Estimated impact on fair value of a 10% increase $ (7) $ (8)  
Estimated impact on fair value of a 20% increase $ (13) $ (16)  
Weighted-Average Coupon Interest Rate 3.90% 4.20%  
Weighted-average servicing fee (basis points) | basis_point 27.5 27.3  
Weighted-average remaining maturity (months) 287 months 278 months  
Residential Mortgage [Member]      
Servicing Assets at Fair Value [Line Items]      
Servicing related fees and other ancillary income $ 95 $ 102 $ 95