Fair Value of Assets and Liabilities (Balances of Assets and Liabilities Measured at Fair Value on a Recurring Basis) (Details) - USD ($) $ in Millions		Dec. 31, 2024		Dec. 31, 2023
Assets, Fair Value Disclosure [Abstract]
Fixed maturity securities available-for-sale		$ 77,617	[1]	$ 60,467	[2]
Equity Method Investments, Fair Value Disclosure		155	[1]	139	[2]
Fair Value Measured On Recurring Basis Funds Held Under Reinsurance Agreements Asset Embedded Derivatives		(215)	[1]	(377)	[2]
Funds Held Under Reinsurance Agreements, Asset Fair Value Disclosure		56	[1]	54	[2]
Cash and Cash Equivalents, Fair Value Disclosure		2,055	[1]	1,335	[2]
Fair Value Measured On Recurring Basis Short Term Investments		313	[1]	187	[2]
Derivative Assets (Liabilities), at Fair Value, Net		121	[1]	97	[2]
Investments, Fair Value Disclosure		138	[1]	119	[2]
Derivative Asset	[1]	2
Assets, Fair Value Disclosure		80,121	[1]	61,924	[2]
Liabilities, Fair Value Disclosure [Abstract]
Fair Value Measured On Recurring Basis Guaranteed Interest Contracts Embedded Derivatives		435		415
Derivative Liability		(160)		(206)
Funds Held under Reinsurance Agreements, Liability		(5,017)		(4,483)
Other Liabilities, Fair Value Disclosure		486		197
Financial Liabilities Fair Value Disclosure		761		406
Fair Value, Net Asset (Liability)		966		856
Fair Value, Inputs, Level 1 [Member]
Assets, Fair Value Disclosure [Abstract]
Fixed maturity securities available-for-sale		2,379	[1]	2,426	[2]
Equity Method Investments, Fair Value Disclosure		67	[1]	69	[2]
Fair Value Measured On Recurring Basis Funds Held Under Reinsurance Agreements Asset Embedded Derivatives		0	[1]	0	[2]
Funds Held Under Reinsurance Agreements, Asset Fair Value Disclosure		0	[1]	0	[2]
Cash and Cash Equivalents, Fair Value Disclosure		2,053	[1]	1,322	[2]
Fair Value Measured On Recurring Basis Short Term Investments		175	[1]	90	[2]
Derivative Assets (Liabilities), at Fair Value, Net		0	[1]	0	[2]
Investments, Fair Value Disclosure		0	[1]	0	[2]
Derivative Asset	[1]	0
Assets, Fair Value Disclosure		4,674	[1]	3,907	[2]
Liabilities, Fair Value Disclosure [Abstract]
Fair Value Measured On Recurring Basis Guaranteed Interest Contracts Embedded Derivatives		0		0
Derivative Liability		0		0
Other Liabilities, Fair Value Disclosure		0		0
Financial Liabilities Fair Value Disclosure		0		0
Fair Value, Inputs, Level 2 [Member]
Assets, Fair Value Disclosure [Abstract]
Fixed maturity securities available-for-sale		66,550	[1]	51,622	[2]
Equity Method Investments, Fair Value Disclosure		0	[1]	0	[2]
Fair Value Measured On Recurring Basis Funds Held Under Reinsurance Agreements Asset Embedded Derivatives		0	[1]	0	[2]
Funds Held Under Reinsurance Agreements, Asset Fair Value Disclosure		0	[1]	0	[2]
Cash and Cash Equivalents, Fair Value Disclosure		2	[1]	13	[2]
Fair Value Measured On Recurring Basis Short Term Investments		127	[1]	95	[2]
Derivative Assets (Liabilities), at Fair Value, Net		121	[1]	97	[2]
Investments, Fair Value Disclosure		138	[1]	119	[2]
Derivative Asset	[1]	0
Assets, Fair Value Disclosure		66,817	[1]	51,849	[2]
Liabilities, Fair Value Disclosure [Abstract]
Fair Value Measured On Recurring Basis Guaranteed Interest Contracts Embedded Derivatives		0		0
Derivative Liability		0		0
Other Liabilities, Fair Value Disclosure		484		197
Financial Liabilities Fair Value Disclosure		484		197
Fair Value, Inputs, Level 3 [Member]
Assets, Fair Value Disclosure [Abstract]
Fixed maturity securities available-for-sale		8,688	[1]	6,419	[2]
Equity Method Investments, Fair Value Disclosure		88	[1]	70	[2]
Fair Value Measured On Recurring Basis Funds Held Under Reinsurance Agreements Asset Embedded Derivatives		(215)	[1]	(377)	[2]
Funds Held Under Reinsurance Agreements, Asset Fair Value Disclosure		56	[1]	54	[2]
Cash and Cash Equivalents, Fair Value Disclosure		0	[1]	0	[2]
Fair Value Measured On Recurring Basis Short Term Investments		11	[1]	2	[2]
Derivative Assets (Liabilities), at Fair Value, Net		0	[1]	0	[2]
Investments, Fair Value Disclosure		0	[1]	0	[2]
Derivative Asset	[1]	2
Assets, Fair Value Disclosure		8,630	[1]	6,168	[2]
Liabilities, Fair Value Disclosure [Abstract]
Fair Value Measured On Recurring Basis Guaranteed Interest Contracts Embedded Derivatives		435		415
Derivative Liability		(160)		(206)
Other Liabilities, Fair Value Disclosure		2		0
Financial Liabilities Fair Value Disclosure		277		209
Fair Value Option Contractholder Directed Unit Linked Investments [Member]
Assets, Fair Value Disclosure [Abstract]
Investments, Fair Value Disclosure		17	[1]	22	[2]
Fair Value Option Contractholder Directed Unit Linked Investments [Member] | Fair Value, Inputs, Level 1 [Member]
Assets, Fair Value Disclosure [Abstract]
Investments, Fair Value Disclosure		0	[1]	0	[2]
Fair Value Option Contractholder Directed Unit Linked Investments [Member] | Fair Value, Inputs, Level 2 [Member]
Assets, Fair Value Disclosure [Abstract]
Investments, Fair Value Disclosure		17	[1]	22	[2]
Fair Value Option Contractholder Directed Unit Linked Investments [Member] | Fair Value, Inputs, Level 3 [Member]
Assets, Fair Value Disclosure [Abstract]
Investments, Fair Value Disclosure		0	[1]	0	[2]
Corporate Debt Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Fixed maturity securities available-for-sale		50,991	[1]	38,755	[2]
Corporate Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Assets, Fair Value Disclosure [Abstract]
Fixed maturity securities available-for-sale		0	[1]	0	[2]
Corporate Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Assets, Fair Value Disclosure [Abstract]
Fixed maturity securities available-for-sale		44,137	[1]	33,822	[2]
Corporate Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Assets, Fair Value Disclosure [Abstract]
Fixed maturity securities available-for-sale		6,854	[1]	4,933	[2]
Canadian Provincial Governments [Member]
Assets, Fair Value Disclosure [Abstract]
Fixed maturity securities available-for-sale		5,016	[1]	3,917	[2]
Canadian Provincial Governments [Member] | Fair Value, Inputs, Level 1 [Member]
Assets, Fair Value Disclosure [Abstract]
Fixed maturity securities available-for-sale		0	[1]	0	[2]
Canadian Provincial Governments [Member] | Fair Value, Inputs, Level 2 [Member]
Assets, Fair Value Disclosure [Abstract]
Fixed maturity securities available-for-sale		5,016	[1]	3,917	[2]
Canadian Provincial Governments [Member] | Fair Value, Inputs, Level 3 [Member]
Assets, Fair Value Disclosure [Abstract]
Fixed maturity securities available-for-sale		0	[1]	0	[2]
Residential Mortgage Backed Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Fixed maturity securities available-for-sale		1,317	[1]	1,079	[2]
Residential Mortgage Backed Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Assets, Fair Value Disclosure [Abstract]
Fixed maturity securities available-for-sale		0	[1]	0	[2]
Residential Mortgage Backed Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Assets, Fair Value Disclosure [Abstract]
Fixed maturity securities available-for-sale		1,317	[1]	1,078	[2]
Residential Mortgage Backed Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Assets, Fair Value Disclosure [Abstract]
Fixed maturity securities available-for-sale		0	[1]	1	[2]
Asset-backed Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Fixed maturity securities available-for-sale		5,040	[1]	4,429	[2]
Assets, Fair Value Disclosure		564		268
Asset-backed Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Assets, Fair Value Disclosure [Abstract]
Fixed maturity securities available-for-sale		0	[1]	0	[2]
Asset-backed Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Assets, Fair Value Disclosure [Abstract]
Fixed maturity securities available-for-sale		3,254	[1]	3,064	[2]
Asset-backed Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Assets, Fair Value Disclosure [Abstract]
Fixed maturity securities available-for-sale		1,786	[1]	1,365	[2]
Commercial Mortgage Backed Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Fixed maturity securities available-for-sale		2,267	[1]	1,773	[2]
Commercial Mortgage Backed Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Assets, Fair Value Disclosure [Abstract]
Fixed maturity securities available-for-sale		0	[1]	0	[2]
Commercial Mortgage Backed Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Assets, Fair Value Disclosure [Abstract]
Fixed maturity securities available-for-sale		2,254	[1]	1,714	[2]
Commercial Mortgage Backed Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Assets, Fair Value Disclosure [Abstract]
Fixed maturity securities available-for-sale		13	[1]	59	[2]
US Treasury and Government [Member]
Assets, Fair Value Disclosure [Abstract]
Fixed maturity securities available-for-sale		2,464	[1]	2,520	[2]
US Treasury and Government [Member] | Fair Value, Inputs, Level 1 [Member]
Assets, Fair Value Disclosure [Abstract]
Fixed maturity securities available-for-sale		2,379	[1]	2,426	[2]
US Treasury and Government [Member] | Fair Value, Inputs, Level 2 [Member]
Assets, Fair Value Disclosure [Abstract]
Fixed maturity securities available-for-sale		80	[1]	87	[2]
US Treasury and Government [Member] | Fair Value, Inputs, Level 3 [Member]
Assets, Fair Value Disclosure [Abstract]
Fixed maturity securities available-for-sale		5	[1]	7	[2]
US States and Political Subdivisions Debt Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Fixed maturity securities available-for-sale		693	[1]	1,114	[2]
US States and Political Subdivisions Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Assets, Fair Value Disclosure [Abstract]
Fixed maturity securities available-for-sale		0	[1]	0	[2]
US States and Political Subdivisions Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Assets, Fair Value Disclosure [Abstract]
Fixed maturity securities available-for-sale		693	[1]	1,095	[2]
US States and Political Subdivisions Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Assets, Fair Value Disclosure [Abstract]
Fixed maturity securities available-for-sale		0	[1]	19	[2]
Debt Security, Government, Non-US [Member]
Assets, Fair Value Disclosure [Abstract]
Fixed maturity securities available-for-sale		5,384	[1]	3,749	[2]
Debt Security, Government, Non-US [Member] | Fair Value, Inputs, Level 1 [Member]
Assets, Fair Value Disclosure [Abstract]
Fixed maturity securities available-for-sale		0	[1]	0	[2]
Debt Security, Government, Non-US [Member] | Fair Value, Inputs, Level 2 [Member]
Assets, Fair Value Disclosure [Abstract]
Fixed maturity securities available-for-sale		5,354	[1]	3,714	[2]
Debt Security, Government, Non-US [Member] | Fair Value, Inputs, Level 3 [Member]
Assets, Fair Value Disclosure [Abstract]
Fixed maturity securities available-for-sale		30	[1]	35	[2]
Japanese Government Debt Securities Member
Assets, Fair Value Disclosure [Abstract]
Fixed maturity securities available-for-sale		4,445		3,131
Japanese Government Debt Securities Member | Fair Value, Inputs, Level 1 [Member]
Assets, Fair Value Disclosure [Abstract]
Fixed maturity securities available-for-sale		0	[1]	0	[2]
Japanese Government Debt Securities Member | Fair Value, Inputs, Level 2 [Member]
Assets, Fair Value Disclosure [Abstract]
Fixed maturity securities available-for-sale		4,445	[1]	3,131	[2]
Japanese Government Debt Securities Member | Fair Value, Inputs, Level 3 [Member]
Assets, Fair Value Disclosure [Abstract]
Fixed maturity securities available-for-sale		$ 0	[1]	$ 0	[2]

[1] Excludes limited partnerships that are measured at estimated fair value using the NAV per share (or its equivalent) as a practical expedient. As of December 31, 2024, the fair value of such investments was $966 million

[2] Excludes limited partnerships that are measured at estimated fair value using the NAV per share (or its equivalent) as a practical expedient. As of December 31, 2023, the fair value of such investments was $856 million.