Investments (Analysis of Past Due Commercial Mortgage and Other Loans) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Financing Receivable, Past Due [Line Items]
Current	$ 63,663	$ 59,940
Total Past Due	17	18
Total Loans	63,680	59,958
Non-Accrual Status	59	87
30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	2	1
60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	0	0
90 days or more past due
Financing Receivable, Past Due [Line Items]
Total Past Due	15	17
Commercial Mortgage Loans
Financing Receivable, Past Due [Line Items]
Current	59,363	55,808
Total Past Due	0	0
Total Loans	59,363	55,808
Non-Accrual Status	44	66
Commercial Mortgage Loans | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	0	0
Commercial Mortgage Loans | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	0	0
Commercial Mortgage Loans | 90 days or more past due
Financing Receivable, Past Due [Line Items]
Total Past Due	0	0
Agricultural property loans
Financing Receivable, Past Due [Line Items]
Current	3,458	3,301
Total Past Due	14	15
Total Loans	3,472	3,316
Non-Accrual Status	13	18
Agricultural property loans | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	1	0
Agricultural property loans | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	0	0
Agricultural property loans | 90 days or more past due
Financing Receivable, Past Due [Line Items]
Total Past Due	13	15
Residential property loans
Financing Receivable, Past Due [Line Items]
Current	121	154
Total Past Due	3	3
Total Loans	124	157
Non-Accrual Status	2	3
Residential property loans | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	1	1
Residential property loans | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	0	0
Residential property loans | 90 days or more past due
Financing Receivable, Past Due [Line Items]
Total Past Due	2	2
Other collateralized loans
Financing Receivable, Past Due [Line Items]
Current	65	17
Total Past Due	0	0
Total Loans	65	17
Non-Accrual Status	0	0
Other collateralized loans | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	0	0
Other collateralized loans | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	0	0
Other collateralized loans | 90 days or more past due
Financing Receivable, Past Due [Line Items]
Total Past Due	0	0
Uncollateralized loans
Financing Receivable, Past Due [Line Items]
Current	656	660
Total Past Due	0	0
Total Loans	656	660
Non-Accrual Status	0	0
Uncollateralized loans | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	0	0
Uncollateralized loans | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	0	0
Uncollateralized loans | 90 days or more past due
Financing Receivable, Past Due [Line Items]
Total Past Due	0	0
Loans | 90 days or more past due
Financing Receivable, Past Due [Line Items]
Accruing Interest	$ 0	$ 0