v3.8.0.1
Investments (Allowance for Credit Losses) (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Allowance for Loan and Lease Losses [Roll Forward]    
Balance, beginning of year $ 106 $ 112
Addition to (release of) allowance for losses 1 (6)
Charge-offs, net of recoveries (1) (1)
Change in foreign exchange 0 1
Total ending balance 106 106
Commercial Mortgage Loans    
Allowance for Loan and Lease Losses [Roll Forward]    
Balance, beginning of year 96 97
Addition to (release of) allowance for losses 2 0
Charge-offs, net of recoveries (1) (1)
Change in foreign exchange 0 0
Total ending balance 97 96
Agricultural Property Loans    
Allowance for Loan and Lease Losses [Roll Forward]    
Balance, beginning of year 2 2
Addition to (release of) allowance for losses 1 0
Charge-offs, net of recoveries 0 0
Change in foreign exchange 0 0
Total ending balance 3 2
Residential property loans    
Allowance for Loan and Lease Losses [Roll Forward]    
Balance, beginning of year 2 3
Addition to (release of) allowance for losses (1) (1)
Charge-offs, net of recoveries 0 0
Change in foreign exchange 0 0
Total ending balance 1 2
Other collateralized loans    
Allowance for Loan and Lease Losses [Roll Forward]    
Balance, beginning of year 0 0
Addition to (release of) allowance for losses 0 0
Charge-offs, net of recoveries 0 0
Change in foreign exchange 0 0
Total ending balance 0 0
Uncollateralized loans    
Allowance for Loan and Lease Losses [Roll Forward]    
Balance, beginning of year 6 10
Addition to (release of) allowance for losses (1) (5)
Charge-offs, net of recoveries 0 0
Change in foreign exchange 0 1
Total ending balance $ 5 $ 6