Investments - Investments - Mortgage Loans by Region and Property Type (Details) - USD ($) $ in Millions	Sep. 30, 2023	Jun. 30, 2023	Dec. 31, 2022	Sep. 30, 2022	Jun. 30, 2022	Dec. 31, 2021
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, after Allowance for Credit Loss	$ 6,016		$ 6,000
Commercial Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 6,062		$ 6,036
Percent of Total	100.00%		100.00%
Financing Receivable, Allowance for Credit Loss	$ (46)	$ (41)	$ (36)	$ (36)	$ (36)	$ (29)
Financing Receivable, after Allowance for Credit Loss	6,016		6,000
Commercial Loan [Member] | Industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 2,351		$ 2,217
Percent of Total	38.80%		36.70%
Commercial Loan [Member] | Multifamily
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 2,191		$ 2,247
Percent of Total	36.10%		37.20%
Commercial Loan [Member] | Office
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 581		$ 585
Percent of Total	9.60%		9.70%
Commercial Loan [Member] | Retail
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 939		$ 947
Percent of Total	15.50%		15.70%
Commercial Loan [Member] | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 0		$ 40
Percent of Total	0.00%		0.70%
Commercial Loan [Member] | Mortgages [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percent of Total	100.00%		100.00%
Commercial Loan [Member] | East North Central [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 345		$ 317
Commercial Loan [Member] | East North Central [Member] | Mortgages [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percent of Total	5.70%		5.30%
Commercial Loan [Member] | Middle Atlantic [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 231		$ 316
Commercial Loan [Member] | Middle Atlantic [Member] | Mortgages [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percent of Total	3.80%		5.20%
Commercial Loan [Member] | Mountain [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 723		$ 707
Commercial Loan [Member] | Mountain [Member] | Mortgages [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percent of Total	11.90%		11.70%
Commercial Loan [Member] | New England [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 352		$ 395
Commercial Loan [Member] | New England [Member] | Mortgages [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percent of Total	5.80%		6.50%
Commercial Loan [Member] | Pacific [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 1,330		$ 1,299
Commercial Loan [Member] | Pacific [Member] | Mortgages [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percent of Total	21.90%		21.50%
Commercial Loan [Member] | South Atlantic [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 1,769		$ 1,670
Commercial Loan [Member] | South Atlantic [Member] | Mortgages [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percent of Total	29.20%		27.70%
Commercial Loan [Member] | West North Central [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 119		$ 105
Commercial Loan [Member] | West North Central [Member] | Mortgages [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percent of Total	2.00%		1.70%
Commercial Loan [Member] | West South Central [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 434		$ 421
Commercial Loan [Member] | West South Central [Member] | Mortgages [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percent of Total	7.20%		7.00%
Commercial Loan [Member] | Region Others [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 759		$ 806
Commercial Loan [Member] | Region Others [Member] | Mortgages [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percent of Total	12.50%		13.40%