Investments (Mortgage Loans - Narrative) (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019	Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unamortized Loan Commitment and Origination Fees and Unamortized Discounts or Premiums	$ 973,000,000		$ 973,000,000		$ 867,000,000
Financing Receivable, Purchase	$ 417,000,000	$ 567,000,000	$ 1,700,000,000	$ 1,900,000,000
Percentage of Mortgage Loans Classified as Performing	99.00%		99.00%		99.00%
Financing Receivable, Nonaccrual	$ 727,000,000		$ 727,000,000		$ 731,000,000
Commercial Mortgage Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Interest Receivable	189,000,000		189,000,000		188,000,000
Deferred mortgage loan interest and principal payments	64,000,000		64,000,000
Financing Receivable, Nonaccrual	174,000,000		174,000,000		176,000,000	$ 176,000,000
Financing Receivable, Nonaccrual, No Allowance	0		0		0
Residential Mortgage Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Interest Receivable	103,000,000		103,000,000		94,000,000
Deferred mortgage loan interest and principal payments	18,000,000		18,000,000
Financing Receivable, Nonaccrual	354,000,000		354,000,000		418,000,000	436,000,000
Financing Receivable, Nonaccrual, No Allowance	0		0		0
Agricultural Mortgage Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Interest Receivable	179,000,000		179,000,000		186,000,000
Deferred mortgage loan interest and principal payments	9,000,000		9,000,000
Financing Receivable, Nonaccrual	199,000,000		199,000,000		137,000,000	$ 105,000,000
Financing Receivable, Nonaccrual, No Allowance	$ 144,000,000		$ 144,000,000		$ 93,000,000