Investments (Investments in Fixed Maturity and Equity Securities Available-for-Sale by Sector) (Details) - USD ($) $ in Millions	Dec. 31, 2024		Dec. 31, 2023		Dec. 31, 2022
Debt Securities, Available-for-sale [Line Items]
Financing Receivable, Allowance for Credit Loss	$ 98		$ 75
Available for Sale at Fair value - Amortized cost	82,907		64,977
Fixed maturity securities available-for-sale at fair value (amortized cost of $82,907 and $64,977; allowance for credit losses of $98 and $75)	77,617	[1]	60,467	[2]
Debt Securities, Available-for-Sale, Allowance for Credit Loss	$ 98		$ 75		$ 37
Fixed Maturities [Member]
Debt Securities, Available-for-sale [Line Items]
Percentage Of Total Available For Sale Securities	100.00%		100.00%
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	$ 6,393		$ 5,560
Available for Sale at Fair value - Amortized cost	82,907		64,977
Fixed maturity securities available-for-sale at fair value (amortized cost of $82,907 and $64,977; allowance for credit losses of $98 and $75)	77,617		60,467
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	1,201		1,125
Debt Securities, Available-for-Sale, Allowance for Credit Loss	98		75
Corporate Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Available for Sale at Fair value - Amortized cost	54,705		42,014
Fixed maturity securities available-for-sale at fair value (amortized cost of $82,907 and $64,977; allowance for credit losses of $98 and $75)	50,991	[1]	38,755	[2]
Debt Securities, Available-for-Sale, Allowance for Credit Loss	$ 82		$ 62		27
Corporate Debt Securities [Member] | Fixed Maturities [Member]
Debt Securities, Available-for-sale [Line Items]
Percentage Of Total Available For Sale Securities	65.70%		64.10%
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	$ 4,274		$ 3,751
Available for Sale at Fair value - Amortized cost	54,705		42,014
Fixed maturity securities available-for-sale at fair value (amortized cost of $82,907 and $64,977; allowance for credit losses of $98 and $75)	50,991		38,755
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	642		554
Debt Securities, Available-for-Sale, Allowance for Credit Loss	82		62
Canadian Provincial Governments [Member]
Debt Securities, Available-for-sale [Line Items]
Fixed maturity securities available-for-sale at fair value (amortized cost of $82,907 and $64,977; allowance for credit losses of $98 and $75)	$ 5,016	[1]	$ 3,917	[2]
Canadian Provincial Governments [Member] | Fixed Maturities [Member]
Debt Securities, Available-for-sale [Line Items]
Percentage Of Total Available For Sale Securities	6.50%		6.50%
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	$ 51		$ 33
Available for Sale at Fair value - Amortized cost	4,655		3,477
Fixed maturity securities available-for-sale at fair value (amortized cost of $82,907 and $64,977; allowance for credit losses of $98 and $75)	5,016		3,917
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	412		473
Debt Securities, Available-for-Sale, Allowance for Credit Loss	0		0
Residential Mortgage Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Fixed maturity securities available-for-sale at fair value (amortized cost of $82,907 and $64,977; allowance for credit losses of $98 and $75)	$ 1,317	[1]	$ 1,079	[2]
Residential Mortgage Backed Securities [Member] | Fixed Maturities [Member]
Debt Securities, Available-for-sale [Line Items]
Percentage Of Total Available For Sale Securities	6.50%		7.30%
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	$ 184		$ 239
Available for Sale at Fair value - Amortized cost	5,197		4,661
Fixed maturity securities available-for-sale at fair value (amortized cost of $82,907 and $64,977; allowance for credit losses of $98 and $75)	5,040		4,429
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	42		19
Debt Securities, Available-for-Sale, Allowance for Credit Loss	15		12
Asset-backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Fixed maturity securities available-for-sale at fair value (amortized cost of $82,907 and $64,977; allowance for credit losses of $98 and $75)	5,040	[1]	4,429	[2]
Debt Securities, Available-for-Sale, Allowance for Credit Loss	$ 15		$ 12		10
Asset-backed Securities [Member] | Fixed Maturities [Member]
Debt Securities, Available-for-sale [Line Items]
Percentage Of Total Available For Sale Securities	2.90%		2.90%
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	$ 98		$ 202
Available for Sale at Fair value - Amortized cost	2,344		1,969
Fixed maturity securities available-for-sale at fair value (amortized cost of $82,907 and $64,977; allowance for credit losses of $98 and $75)	2,267		1,773
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	22		7
Debt Securities, Available-for-Sale, Allowance for Credit Loss	1		1
Commercial Mortgage Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Fixed maturity securities available-for-sale at fair value (amortized cost of $82,907 and $64,977; allowance for credit losses of $98 and $75)	2,267	[1]	1,773	[2]
Debt Securities, Available-for-Sale, Allowance for Credit Loss	$ 1		$ 1		$ 0
Commercial Mortgage Backed Securities [Member] | Fixed Maturities [Member]
Debt Securities, Available-for-sale [Line Items]
Percentage Of Total Available For Sale Securities	1.70%		1.80%
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	$ 107		$ 102
Available for Sale at Fair value - Amortized cost	1,412		1,173
Fixed maturity securities available-for-sale at fair value (amortized cost of $82,907 and $64,977; allowance for credit losses of $98 and $75)	1,317		1,079
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	12		8
Debt Securities, Available-for-Sale, Allowance for Credit Loss	0		0
US Treasury and Government [Member]
Debt Securities, Available-for-sale [Line Items]
Fixed maturity securities available-for-sale at fair value (amortized cost of $82,907 and $64,977; allowance for credit losses of $98 and $75)	$ 2,464	[1]	$ 2,520	[2]
US Treasury and Government [Member] | Fixed Maturities [Member]
Debt Securities, Available-for-sale [Line Items]
Percentage Of Total Available For Sale Securities	3.20%		4.20%
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	$ 281		$ 214
Available for Sale at Fair value - Amortized cost			2,725
Fixed maturity securities available-for-sale at fair value (amortized cost of $82,907 and $64,977; allowance for credit losses of $98 and $75)	2,464		2,520
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	11		9
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]
Fixed maturity securities available-for-sale at fair value (amortized cost of $82,907 and $64,977; allowance for credit losses of $98 and $75)	$ 693	[1]	$ 1,114	[2]
US States and Political Subdivisions Debt Securities [Member] | Fixed Maturities [Member]
Debt Securities, Available-for-sale [Line Items]
Percentage Of Total Available For Sale Securities	0.90%		1.80%
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	$ 99		$ 129
Available for Sale at Fair value - Amortized cost	789		1,236
Fixed maturity securities available-for-sale at fair value (amortized cost of $82,907 and $64,977; allowance for credit losses of $98 and $75)	693		1,114
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	3		7
Debt Securities, Available-for-Sale, Allowance for Credit Loss	0		0
Debt Security, Government, Non-US [Member]
Debt Securities, Available-for-sale [Line Items]
Fixed maturity securities available-for-sale at fair value (amortized cost of $82,907 and $64,977; allowance for credit losses of $98 and $75)	$ 5,384	[1]	$ 3,749	[2]
Debt Security, Government, Non-US [Member] | Fixed Maturities [Member]
Debt Securities, Available-for-sale [Line Items]
Percentage Of Total Available For Sale Securities	6.90%		6.20%
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	$ 424		$ 388
Available for Sale at Fair value - Amortized cost	5,752		4,092
Fixed maturity securities available-for-sale at fair value (amortized cost of $82,907 and $64,977; allowance for credit losses of $98 and $75)	5,384		3,749
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	56		45
Debt Securities, Available-for-Sale, Allowance for Credit Loss	0		0
Japanese Government Debt Securities Member
Debt Securities, Available-for-sale [Line Items]
Fixed maturity securities available-for-sale at fair value (amortized cost of $82,907 and $64,977; allowance for credit losses of $98 and $75)	$ 4,445		$ 3,131
Japanese Government Debt Securities Member | Fixed Maturities [Member]
Debt Securities, Available-for-sale [Line Items]
Percentage Of Total Available For Sale Securities	5.70%		5.20%
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	$ 875		$ 502
Available for Sale at Fair value - Amortized cost			3,630
Fixed maturity securities available-for-sale at fair value (amortized cost of $82,907 and $64,977; allowance for credit losses of $98 and $75)	4,445		3,131
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	1		3
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 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.