Investments (Past Due and Interest Accrual Status of Mortgage Loans) (Details) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019	Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	$ 682	$ 591
Greater than 90 Days Past Due and Still Accruing	133	51
Financing Receivable, Nonaccrual	727	731
Commercial Mortgage Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	8	10
Greater than 90 Days Past Due and Still Accruing	6	9
Financing Receivable, Nonaccrual	174	176	$ 176
Residential Mortgage Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	397	452
Greater than 90 Days Past Due and Still Accruing	43	35
Financing Receivable, Nonaccrual	354	418	436
Agricultural Mortgage Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	277	129
Greater than 90 Days Past Due and Still Accruing	84	7
Financing Receivable, Nonaccrual	$ 199	$ 137	$ 105