Investments (Investments in Fixed Maturity and Equity Securities Available-for-Sale by Sector) (Details) - USD ($) $ in Millions	Jun. 30, 2025		Mar. 31, 2025	Dec. 31, 2024		Jun. 30, 2024	Mar. 31, 2024	Dec. 31, 2023
Debt Securities, Available-for-sale [Line Items]
Available for Sale at Fair value - Amortized cost	$ 91,888			$ 82,907
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	1,227			1,201
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	6,940			6,393
Fixed maturity securities, available-for-sale	$ 86,043	[1]		$ 77,617	[2]
% of Total	100.00%			100.00%
Debt Securities, Available-for-Sale, Allowance for Credit Loss	$ 132		$ 103	$ 98		$ 111	$ 95	$ 75
Corporate Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Available for Sale at Fair value - Amortized cost	61,006			54,705
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	706			642
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	4,274			4,274
Fixed maturity securities, available-for-sale	$ 57,326	[1]		$ 50,991	[2]
% of Total	66.50%			65.70%
Debt Securities, Available-for-Sale, Allowance for Credit Loss	$ 112		88	$ 82		95	79	62
Canadian and Canadian provincial governments
Debt Securities, Available-for-sale [Line Items]
Available for Sale at Fair value - Amortized cost	4,871			4,655
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	344			412
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	81			51
Fixed maturity securities, available-for-sale	$ 5,134	[1]		$ 5,016	[2]
% of Total	6.00%			6.50%
Debt Securities, Available-for-Sale, Allowance for Credit Loss	$ 0			$ 0
Residential mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Available for Sale at Fair value - Amortized cost	1,593			1,412
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	15			12
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	86			107
Fixed maturity securities, available-for-sale	$ 1,522	[1]		$ 1,317	[2]
% of Total	1.80%			1.70%
Debt Securities, Available-for-Sale, Allowance for Credit Loss	$ 0			$ 0
Asset-backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Available for Sale at Fair value - Amortized cost	6,160			5,197
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	40			42
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	165			184
Fixed maturity securities, available-for-sale	$ 6,016	[1]		$ 5,040	[2]
% of Total	7.00%			6.50%
Debt Securities, Available-for-Sale, Allowance for Credit Loss	$ 19		15	$ 15		15	15	12
Commercial Mortgage Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Available for Sale at Fair value - Amortized cost	2,129			2,344
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	24			22
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	76			98
Fixed maturity securities, available-for-sale	$ 2,076	[1]		$ 2,267	[2]
% of Total	2.40%			2.90%
Debt Securities, Available-for-Sale, Allowance for Credit Loss	$ 1		$ 0	$ 1		$ 1	$ 1	$ 1
US Treasury and Government [Member]
Debt Securities, Available-for-sale [Line Items]
Available for Sale at Fair value - Amortized cost	1,618			2,734
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	9			11
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	257			281
Fixed maturity securities, available-for-sale	$ 1,370	[1]		$ 2,464	[2]
% of Total	1.60%			3.20%
Debt Securities, Available-for-Sale, Allowance for Credit Loss	$ 0			$ 0
US States and Political Subdivisions Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Available for Sale at Fair value - Amortized cost	786			789
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	2			3
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	89			99
Fixed maturity securities, available-for-sale	$ 699	[1]		$ 693	[2]
% of Total	0.80%			0.90%
Debt Securities, Available-for-Sale, Allowance for Credit Loss	$ 0			$ 0
Debt Security, Government, Non-US [Member]
Debt Securities, Available-for-sale [Line Items]
Available for Sale at Fair value - Amortized cost	6,521			5,752
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	87			56
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	446			424
Fixed maturity securities, available-for-sale	$ 6,162	[1]		$ 5,384	[2]
% of Total	7.20%			6.90%
Debt Securities, Available-for-Sale, Allowance for Credit Loss	$ 0			$ 0
JAPAN
Debt Securities, Available-for-sale [Line Items]
Available for Sale at Fair value - Amortized cost	7,204			5,319
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	0			1
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	1,466			875
Fixed maturity securities, available-for-sale	$ 5,738			$ 4,445
% of Total	6.70%			5.70%
Debt Securities, Available-for-Sale, Allowance for Credit Loss	$ 0			$ 0

[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, 2025, the fair value of such investments was $954 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, 2024, the fair value of such investments was $966 million