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Investments (Evaluation of Available-For-Sale Securities for OTTI and Evaluating Temporarily Impaired AFS Securities - Narrative) (Details)
$ in Millions
12 Months Ended
Dec. 31, 2019
USD ($)
Contracts
Dec. 31, 2018
USD ($)
Dec. 31, 2017
USD ($)
Debt Securities, Available-for-sale [Line Items]      
Change in Gross Unrealized Temporary Loss $ (14,591) $ 8,719 $ (4,623)
Debt Securities Available For Sale With Gross Unrealized Loss Of Equal To Or Greater Than Stated Percentage 20.00%    
Fixed Maturity Securities      
Debt Securities, Available-for-sale [Line Items]      
Change in Gross Unrealized Temporary Loss $ 4,300    
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss 1,600    
20% or more | Six months or greater | Fixed Maturity Securities      
Debt Securities, Available-for-sale [Line Items]      
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss $ 161    
Number of Securities | Contracts 70    
20% or more | Six months or greater | Fixed Maturity Securities | Investment Grade      
Debt Securities, Available-for-sale [Line Items]      
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss $ 92    
Number of Securities | Contracts 23    
Percentage of gross unrealized loss 57.00%    
20% or more | Six months or greater | Fixed Maturity Securities | Below Investment Grade      
Debt Securities, Available-for-sale [Line Items]      
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss $ 69    
Number of Securities | Contracts 47    
Percentage of gross unrealized loss 43.00%