v3.8.0.1
Fair Value of Assets and Liabilities (Changes in Level 3 Derivative Assets and Liabilities) (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Equity      
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]      
Fair Value, beginning of period $ 0 $ 32 $ 6
Total gains (losses) (realized/unrealized) included in earnings:      
Realized investment gains (losses), net 0 0 20
Other income 0 0 0
Purchases 0 0 9
Sales 0 0 (2)
Issuances 0 0 0
Settlements 0 0 0
Foreign currency translation 0    
Other 10 (32) 0
Transfers into Level 3 0 0 0
Transfers out of Level 3 0 0 (1)
Fair Value, end of period 10 0 32
Unrealized gains (losses) for assets still held included in earnings:      
Realized investment gains (losses), net 0 0 20
Other income 0 0 0
Interest Rate      
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]      
Fair Value, beginning of period 4 5 3
Total gains (losses) (realized/unrealized) included in earnings:      
Realized investment gains (losses), net (7) (1) 2
Other income 0 0 0
Purchases 0 0 0
Sales 0 0 0
Issuances 0 0 0
Settlements 0 0 0
Foreign currency translation 0    
Other 0 0 0
Transfers into Level 3 0 0 0
Transfers out of Level 3 0 0 0
Fair Value, end of period (3) 4 5
Unrealized gains (losses) for assets still held included in earnings:      
Realized investment gains (losses), net (7) 0 2
Other income $ 0 $ 0 $ 0