Investments (Mortgage Loans by Maturity Date) (Details) - USD ($) $ in Millions	Sep. 30, 2025	Dec. 31, 2024
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 10,652	$ 8,952
Mortgage Loans On Real Estate Commercial And Consumer Net Percentage Of Total	100.00%	100.00%
Commercial Real Estate
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 10,408	$ 8,952
Mortgage Loans On Real Estate Commercial And Consumer Net Percentage Of Total	97.70%	100.00%
Residential Real Estate
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 244	$ 0
Mortgage Loans On Real Estate Commercial And Consumer Net Percentage Of Total	100.00%	0.00%
Due within five years | Commercial Real Estate
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 4,441	$ 3,984
Mortgage Loans On Real Estate Commercial And Consumer Net Percentage Of Total	42.70%	44.50%
Due within five years | Residential Real Estate
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 158	$ 0
Mortgage Loans On Real Estate Commercial And Consumer Net Percentage Of Total	64.80%	0.00%
Due after five years through ten years | Commercial Real Estate
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 5,093	$ 3,959
Mortgage Loans On Real Estate Commercial And Consumer Net Percentage Of Total	48.90%	44.20%
Due after five years through ten years | Residential Real Estate
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 0	$ 0
Mortgage Loans On Real Estate Commercial And Consumer Net Percentage Of Total	0.00%	0.00%
Due after ten years | Commercial Real Estate
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 874	$ 1,009
Mortgage Loans On Real Estate Commercial And Consumer Net Percentage Of Total	8.40%	11.30%
Due after ten years | Residential Real Estate
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 86	$ 0
Mortgage Loans On Real Estate Commercial And Consumer Net Percentage Of Total	35.20%	0.00%