Investments (Past Due and Interest Accrual Status of Mortgage Loans) (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	$ 571	$ 684
Greater than 90 Days Past Due and Still Accruing Interest	94	153
Nonaccrual	676	717
Agricultural Mortgage Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	134	204
Greater than 90 Days Past Due and Still Accruing Interest	52	109
Nonaccrual	105	105
Commercial Mortgage Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	4	9
Greater than 90 Days Past Due and Still Accruing Interest	4	9
Nonaccrual	176	176
Residential Mortgage Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	433	471
Greater than 90 Days Past Due and Still Accruing Interest	38	35
Nonaccrual	$ 395	$ 436