Investments (Past Due and Interest Accrual Status of Mortgage Loans) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	$ 591	$ 684
Greater than 90 Days Past Due and Still Accruing Interest	51	153
Nonaccrual	731	717
Commercial Mortgage Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	10	9
Greater than 90 Days Past Due and Still Accruing Interest	9	9
Nonaccrual	176	176
Residential Mortgage Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	452	471
Greater than 90 Days Past Due and Still Accruing Interest	35	35
Nonaccrual	418	436
Agricultural Mortgage Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	129	204
Greater than 90 Days Past Due and Still Accruing Interest	7	109
Nonaccrual	$ 137	$ 105