Investments (Analysis of Past Due Commercial Mortgage and Other Loans) (Details) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Financing Receivable, Past Due [Line Items]
Total Loans	$ 64,531	$ 65,660
Non-Accrual Status	20	21
Current
Financing Receivable, Past Due [Line Items]
Total Loans	64,465	65,484
30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Loans	50	41
60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Loans	0	119
90 days or more past due
Financing Receivable, Past Due [Line Items]
Total Loans	16	16
Total Past Due
Financing Receivable, Past Due [Line Items]
Total Loans	66	176
Commercial Mortgage Loans
Financing Receivable, Past Due [Line Items]
Total Loans	59,638	60,736
Non-Accrual Status	2	5
Commercial Mortgage Loans | Current
Financing Receivable, Past Due [Line Items]
Total Loans	59,638	60,614
Commercial Mortgage Loans | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Loans	0	3
Commercial Mortgage Loans | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Loans	0	119
Commercial Mortgage Loans | 90 days or more past due
Financing Receivable, Past Due [Line Items]
Total Loans	0	0
Commercial Mortgage Loans | Total Past Due
Financing Receivable, Past Due [Line Items]
Total Loans	0	122
Agricultural property loans
Financing Receivable, Past Due [Line Items]
Total Loans	4,162	4,048
Non-Accrual Status	17	15
Agricultural property loans | Current
Financing Receivable, Past Due [Line Items]
Total Loans	4,098	3,996
Agricultural property loans | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Loans	49	37
Agricultural property loans | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Loans	0	0
Agricultural property loans | 90 days or more past due
Financing Receivable, Past Due [Line Items]
Total Loans	15	15
Agricultural property loans | Total Past Due
Financing Receivable, Past Due [Line Items]
Total Loans	64	52
Residential Property Loans
Financing Receivable, Past Due [Line Items]
Total Loans	81	101
Non-Accrual Status	1	1
Residential Property Loans | Current
Financing Receivable, Past Due [Line Items]
Total Loans	79	99
Residential Property Loans | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Loans	1	1
Residential Property Loans | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Loans	0	0
Residential Property Loans | 90 days or more past due
Financing Receivable, Past Due [Line Items]
Total Loans	1	1
Residential Property Loans | Total Past Due
Financing Receivable, Past Due [Line Items]
Total Loans	2	2
Other Collateralized Loans
Financing Receivable, Past Due [Line Items]
Total Loans	71	120
Non-Accrual Status	0	0
Other Collateralized Loans | Current
Financing Receivable, Past Due [Line Items]
Total Loans	71	120
Other Collateralized Loans | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Loans	0	0
Other Collateralized Loans | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Loans	0	0
Other Collateralized Loans | 90 days or more past due
Financing Receivable, Past Due [Line Items]
Total Loans	0	0
Other Collateralized Loans | Total Past Due
Financing Receivable, Past Due [Line Items]
Total Loans	0	0
Uncollateralized loans
Financing Receivable, Past Due [Line Items]
Total Loans	579	655
Non-Accrual Status	0	0
Uncollateralized loans | Current
Financing Receivable, Past Due [Line Items]
Total Loans	579	655
Uncollateralized loans | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Loans	0	0
Uncollateralized loans | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Loans	0	0
Uncollateralized loans | 90 days or more past due
Financing Receivable, Past Due [Line Items]
Total Loans	0	0
Uncollateralized loans | Total Past Due
Financing Receivable, Past Due [Line Items]
Total Loans	0	0
Loans | 90 days or more past due
Financing Receivable, Past Due [Line Items]
Accruing Interest	$ 0	$ 0