Investments (Past Due and Interest Accrual Status of Mortgage Loans) (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022	Dec. 31, 2021
Financing Receivable, Nonaccrual [Line Items]
Mortgage Loans, Gross	$ 92,935	$ 84,290
Greater than 90 Days Past Due and Still Accruing Interest	49	39
Financing Receivable, Nonaccrual	1,018	762
Financial Asset, Past Due
Financing Receivable, Nonaccrual [Line Items]
Mortgage Loans, Gross	612	603
Commercial Mortgage Loans
Financing Receivable, Nonaccrual [Line Items]
Mortgage Loans, Gross	60,051	52,502
Greater than 90 Days Past Due and Still Accruing Interest	17	6
Financing Receivable, Nonaccrual	365	169	$ 155
Commercial Mortgage Loans | Financial Asset, Past Due
Financing Receivable, Nonaccrual [Line Items]
Mortgage Loans, Gross	87	6
Residential Mortgage Loans
Financing Receivable, Nonaccrual [Line Items]
Mortgage Loans, Gross	12,986	12,482
Greater than 90 Days Past Due and Still Accruing Interest	17	12
Financing Receivable, Nonaccrual	418	462	442
Residential Mortgage Loans | Financial Asset, Past Due
Financing Receivable, Nonaccrual [Line Items]
Mortgage Loans, Gross	434	473
Agricultural Mortgage Loans
Financing Receivable, Nonaccrual [Line Items]
Mortgage Loans, Gross	19,898	19,306
Greater than 90 Days Past Due and Still Accruing Interest	15	21
Financing Receivable, Nonaccrual	235	131	$ 225
Agricultural Mortgage Loans | Financial Asset, Past Due
Financing Receivable, Nonaccrual [Line Items]
Mortgage Loans, Gross	$ 91	$ 124