Fair Value of Assets and Liabilities Fair Value of Assets and Liabilities (Balances of Assets and Liabilities Measured at Fair Value on a Recurring Basis) (Details) - USD ($) $ in Millions	Jun. 30, 2024		Dec. 31, 2023
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	$ 70,491	[1]	$ 60,467	[2]
Equity Method Investments, Fair Value Disclosure	144	[1]	139	[2]
Funds withheld at interest embedded derivatives	(274)	[1]	(377)	[2]
Funds Held Under Reinsurance Agreements, Asset Fair Value Disclosure	55	[1]	54	[2]
Cash and cash equivalents	3,030	[1]	1,335	[2]
Short-term investments	304	[1]	187	[2]
Derivative Assets (Liabilities), at Fair Value, Net	66	[1]	97	[2]
Investments, Fair Value Disclosure	85	[1]	119	[2]
Assets, Fair Value Disclosure	73,835	[1]	61,924	[2]
Liabilities Fair Value Disclosure
Fair Value Measured On Recurring Basis Guaranteed Interest Contracts Embedded Derivatives	386		415
Funds Held under Reinsurance Agreements, Liability	(4,323)		(4,483)
Other liabilities	(430)		(197)
Financial Liabilities Fair Value Disclosure	610		406
Fair Value, Net Asset (Liability)	911
Derivative Liability	(206)		(206)
Fair Value Option Contractholder Directed Unit Linked Investments [Member]
Assets Fair Value Disclosure
Investments, Fair Value Disclosure	19	[1]	22	[2]
Corporate Debt Securities [Member]
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	46,131	[1]	38,755	[2]
Canadian and Canadian provincial governments
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	4,780	[1]	3,917	[2]
Residential mortgage-backed securities
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	1,212	[1]	1,079	[2]
Asset-backed Securities [Member]
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	5,143	[1]	4,429	[2]
Assets, Fair Value Disclosure	288		268
Commercial Mortgage Backed Securities [Member]
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	2,120	[1]	1,773	[2]
US Treasury and Government [Member]
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	1,428	[1]	2,520	[2]
US States and Political Subdivisions Debt Securities [Member]
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	1,042	[1]	1,114	[2]
Debt Security, Government, Non-US [Member]
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	4,172	[1]	3,749	[2]
Japanese Government
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	4,463	[1]	3,131	[2]
Fair Value Inputs Level 1 Member
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	1,337	[1]	2,426	[2]
Equity Method Investments, Fair Value Disclosure	70	[1]	69	[2]
Funds withheld at interest embedded derivatives	0	[1]	0	[2]
Funds Held Under Reinsurance Agreements, Asset Fair Value Disclosure	0	[1]	0	[2]
Cash and cash equivalents	3,025	[1]	1,322	[2]
Short-term investments	129	[1]	90	[2]
Derivative Assets (Liabilities), at Fair Value, Net	0	[1]	0	[2]
Investments, Fair Value Disclosure	0	[1]	0	[2]
Assets, Fair Value Disclosure	4,561	[1]	3,907	[2]
Liabilities Fair Value Disclosure
Fair Value Measured On Recurring Basis Guaranteed Interest Contracts Embedded Derivatives	0		0
Other liabilities	0		0
Financial Liabilities Fair Value Disclosure	0		0
Derivative Liability	0		0
Fair Value Inputs Level 1 Member | Fair Value Option Contractholder Directed Unit Linked Investments [Member]
Assets Fair Value Disclosure
Investments, Fair Value Disclosure	0	[1]	0	[2]
Fair Value Inputs Level 1 Member | Corporate Debt Securities [Member]
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	0	[1]	0	[2]
Fair Value Inputs Level 1 Member | Canadian and Canadian provincial governments
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	0	[1]	0	[2]
Fair Value Inputs Level 1 Member | Residential mortgage-backed securities
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	0	[1]	0	[2]
Fair Value Inputs Level 1 Member | Asset-backed Securities [Member]
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	0	[1]	0	[2]
Fair Value Inputs Level 1 Member | Commercial Mortgage Backed Securities [Member]
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	0	[1]	0	[2]
Fair Value Inputs Level 1 Member | US Treasury and Government [Member]
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	1,337	[1]	2,426	[2]
Fair Value Inputs Level 1 Member | US States and Political Subdivisions Debt Securities [Member]
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	0	[1]	0	[2]
Fair Value Inputs Level 1 Member | Debt Security, Government, Non-US [Member]
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	0	[1]	0	[2]
Fair Value Inputs Level 1 Member | Japanese Government
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	0	[1]	0	[2]
Fair Value Inputs Level 2 Member
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	62,098	[1]	51,622	[2]
Equity Method Investments, Fair Value Disclosure	0	[1]	0	[2]
Funds withheld at interest embedded derivatives	0	[1]	0	[2]
Funds Held Under Reinsurance Agreements, Asset Fair Value Disclosure	0	[1]	0	[2]
Cash and cash equivalents	5	[1]	13	[2]
Short-term investments	160	[1]	95	[2]
Derivative Assets (Liabilities), at Fair Value, Net	66	[1]	97	[2]
Investments, Fair Value Disclosure	85	[1]	119	[2]
Assets, Fair Value Disclosure	62,348	[1]	51,849	[2]
Liabilities Fair Value Disclosure
Fair Value Measured On Recurring Basis Guaranteed Interest Contracts Embedded Derivatives	0		0
Other liabilities	(430)		(197)
Financial Liabilities Fair Value Disclosure	430		197
Derivative Liability	0		0
Fair Value Inputs Level 2 Member | Fair Value Option Contractholder Directed Unit Linked Investments [Member]
Assets Fair Value Disclosure
Investments, Fair Value Disclosure	19	[1]	22	[2]
Fair Value Inputs Level 2 Member | Corporate Debt Securities [Member]
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	40,630	[1]	33,822	[2]
Fair Value Inputs Level 2 Member | Canadian and Canadian provincial governments
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	4,780	[1]	3,917	[2]
Fair Value Inputs Level 2 Member | Residential mortgage-backed securities
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	3,679	[1]	1,078	[2]
Fair Value Inputs Level 2 Member | Asset-backed Securities [Member]
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	2,088	[1]	3,064	[2]
Fair Value Inputs Level 2 Member | Commercial Mortgage Backed Securities [Member]
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	1,211	[1]	1,714	[2]
Fair Value Inputs Level 2 Member | US Treasury and Government [Member]
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	85	[1]	87	[2]
Fair Value Inputs Level 2 Member | US States and Political Subdivisions Debt Securities [Member]
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	1,021	[1]	1,095	[2]
Fair Value Inputs Level 2 Member | Debt Security, Government, Non-US [Member]
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	4,141	[1]	3,714	[2]
Fair Value Inputs Level 2 Member | Japanese Government
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	4,463	[1]	3,131	[2]
Fair Value Inputs Level 3 Member
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	7,056	[1]	6,419	[2]
Equity Method Investments, Fair Value Disclosure	74	[1]	70	[2]
Funds withheld at interest embedded derivatives	(274)	[1]	(377)	[2]
Funds Held Under Reinsurance Agreements, Asset Fair Value Disclosure	55	[1]	54	[2]
Cash and cash equivalents	0	[1]	0	[2]
Short-term investments	15	[1]	2	[2]
Derivative Assets (Liabilities), at Fair Value, Net	0	[1]	0	[2]
Investments, Fair Value Disclosure	0	[1]	0	[2]
Assets, Fair Value Disclosure	6,926	[1]	6,168	[2]
Liabilities Fair Value Disclosure
Fair Value Measured On Recurring Basis Guaranteed Interest Contracts Embedded Derivatives	386		415
Other liabilities	0		0
Financial Liabilities Fair Value Disclosure	180		209
Derivative Liability	(206)		(206)
Fair Value Inputs Level 3 Member | Fair Value Option Contractholder Directed Unit Linked Investments [Member]
Assets Fair Value Disclosure
Investments, Fair Value Disclosure	0	[1]	0	[2]
Fair Value Inputs Level 3 Member | Corporate Debt Securities [Member]
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	5,501	[1]	4,933	[2]
Fair Value Inputs Level 3 Member | Canadian and Canadian provincial governments
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	0	[1]	0	[2]
Fair Value Inputs Level 3 Member | Residential mortgage-backed securities
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	1,464	[1]	1	[2]
Fair Value Inputs Level 3 Member | Asset-backed Securities [Member]
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	32	[1]	1,365	[2]
Fair Value Inputs Level 3 Member | Commercial Mortgage Backed Securities [Member]
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	1	[1]	59	[2]
Fair Value Inputs Level 3 Member | US Treasury and Government [Member]
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	6	[1]	7	[2]
Fair Value Inputs Level 3 Member | US States and Political Subdivisions Debt Securities [Member]
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	21	[1]	19	[2]
Fair Value Inputs Level 3 Member | Debt Security, Government, Non-US [Member]
Assets Fair Value Disclosure
Fixed maturity securities, available-for-sale	31	[1]	35	[2]
Fair Value Inputs Level 3 Member | Japanese Government
Assets Fair Value Disclosure
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 June 30, 2024, the fair value of such investments was $911 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