Debt (Schedule of Debt Outstanding) (Details) € in Millions, ¥ in Millions, $ in Millions		Dec. 31, 2024 USD ($)	Dec. 31, 2024 EUR (€)	Dec. 31, 2024 CNY (¥)	Nov. 30, 2024 USD ($)	Dec. 31, 2023 USD ($)	Mar. 31, 2000 USD ($)
Debt Instrument [Line Items]
Weighted average interest rate on short-term debt						4.90%
Repurchase agreements		$ 2,731				$ 2,833
Short-term debt		800				1,460
Long-term debt		14,379				13,035
Hybrid debt		419				308
Variable Interest Entity, Primary Beneficiary
Debt Instrument [Line Items]
Repurchase agreements		$ 815				1,009
Huatai Supplementary Bonds Due December 2034
Debt Instrument [Line Items]
Long-term debt stated interest rate		2.90%	2.90%	2.90%
Hybrid debt		$ 110		¥ 800	$ 111	0
Senior Notes | INA Senior Notes Due March 2025 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount		$ 800
Long-term debt stated interest rate		3.15%	3.15%	3.15%
Long-term debt		$ 0				799
Make Whole Premium Additional Percent		0.15%	0.15%	0.15%
Senior Notes | INA Senior Notes Due May 2026 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount		$ 1,500
Long-term debt stated interest rate		3.35%	3.35%	3.35%
Long-term debt		$ 1,498				1,497
Make Whole Premium Additional Percent		0.20%	0.20%	0.20%
Senior Notes | INA Senior Notes Due June 2027 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount | €			€ 575
Long-term debt stated interest rate		0.875%	0.875%	0.875%
Long-term debt		$ 604				623
Make Whole Premium Additional Percent		0.20%	0.20%	0.20%
Senior Notes | INA Senior Notes Due March 2028 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount | €			€ 900
Long-term debt stated interest rate		1.55%	1.55%	1.55%
Long-term debt		$ 944				974
Make Whole Premium Additional Percent		0.15%	0.15%	0.15%
Senior Notes | INA Senior Notes Due December 2029 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount | €			€ 700
Long-term debt stated interest rate		0.875%	0.875%	0.875%
Long-term debt		$ 734				758
Make Whole Premium Additional Percent		0.20%	0.20%	0.20%
Senior Notes | INA Senior Notes Due September 2030 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount		$ 1,000
Long-term debt stated interest rate		1.375%	1.375%	1.375%
Long-term debt		$ 995				994
Make Whole Premium Additional Percent		0.15%	0.15%	0.15%
Senior Notes | INA Senior Notes Due June 2031 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount | €			€ 575
Long-term debt stated interest rate		1.40%	1.40%	1.40%
Long-term debt		$ 601				621
Make Whole Premium Additional Percent		0.25%	0.25%	0.25%
Senior Notes | INA Senior Notes Due May 2036 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount		$ 300
Long-term debt stated interest rate		6.70%	6.70%	6.70%
Long-term debt		$ 298				298
Make Whole Premium Additional Percent		0.20%	0.20%	0.20%
Senior Notes | INA Senior Notes Due May 2037 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount		$ 800
Long-term debt stated interest rate		6.00%	6.00%	6.00%
Long-term debt		$ 909				918
Make Whole Premium Additional Percent		0.20%	0.20%	0.20%
Senior Notes | INA Senior Notes Due March 2038 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount | €			€ 900
Long-term debt stated interest rate		2.50%	2.50%	2.50%
Long-term debt		$ 940				971
Make Whole Premium Additional Percent		0.25%	0.25%	0.25%
Senior Notes | INA Senior Notes Due May 2038 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount		$ 600
Long-term debt stated interest rate		6.50%	6.50%	6.50%
Long-term debt		$ 710				718
Make Whole Premium Additional Percent		0.30%	0.30%	0.30%
Senior Notes | INA Senior Notes Due March 2043 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount		$ 475
Long-term debt stated interest rate		4.15%	4.15%	4.15%
Long-term debt		$ 471				471
Make Whole Premium Additional Percent		0.15%	0.15%	0.15%
Senior Notes | INA Senior Notes Due November 2045 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount		$ 1,500
Long-term debt stated interest rate		4.35%	4.35%	4.35%
Long-term debt		$ 1,487				1,486
Make Whole Premium Additional Percent		0.25%	0.25%	0.25%
Senior Notes | INA Senior Notes Due December 2051 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount		$ 600
Long-term debt stated interest rate		2.85%	2.85%	2.85%
Long-term debt		$ 594				593
Make Whole Premium Additional Percent		0.15%	0.15%	0.15%
Senior Notes | INA Senior Notes Due December 2061 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount		$ 1,000
Long-term debt stated interest rate		3.05%	3.05%	3.05%
Long-term debt		$ 984				984
Make Whole Premium Additional Percent		0.20%	0.20%	0.20%
Senior Notes | INA Senior Notes Due August 2029
Debt Instrument [Line Items]
Debt Instrument, Face Amount		$ 700
Long-term debt stated interest rate		4.65%	4.65%	4.65%
Long-term debt		$ 695				0
Make Whole Premium Additional Percent		0.15%	0.15%	0.15%
Senior Notes | INA Senior Notes Due March 2034
Debt Instrument [Line Items]
Debt Instrument, Face Amount		$ 1,600
Long-term debt stated interest rate		5.00%	5.00%	5.00%
Long-term debt		$ 1,588				0
Make Whole Premium Additional Percent		0.15%	0.15%	0.15%
Trust Preferred Securities | Chubb INA Capital Securities Due 2030 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount		$ 309					$ 300
Long-term debt stated interest rate		9.70%	9.70%	9.70%			9.70%
Hybrid debt	[1]	$ 309				308
Unsecured Debt | INA Senior Notes Due August 2029 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount		$ 100
Long-term debt stated interest rate		8.875%	8.875%	8.875%
Long-term debt		$ 100				100
Unsecured Debt | INA Senior Notes Due November 2031 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount		$ 200
Long-term debt stated interest rate		6.80%	6.80%	6.80%
Long-term debt		$ 227				$ 230
Make Whole Premium Additional Percent		0.25%	0.25%	0.25%
Repurchase agreements
Debt Instrument [Line Items]
Weighted average interest rate on short-term debt		4.10%	4.10%	4.10%		5.40%
Repurchase agreements		$ 1,916				$ 1,824
Repurchase agreements | Variable Interest Entity, Primary Beneficiary
Debt Instrument [Line Items]
Weighted average interest rate on short-term debt		2.20%	2.20%	2.20%
Repurchase agreements	[2]	$ 815				1,009
Senior Notes | INA Senior Notes Due May 2024 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount		$ 700
Long-term debt stated interest rate		3.35%	3.35%	3.35%
Short-term debt		$ 0				700
Make Whole Premium Additional Percent		0.15%	0.15%	0.15%
Senior Notes | INA Senior Notes Due December 2024 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount | €			€ 700
Long-term debt stated interest rate		0.30%	0.30%	0.30%
Short-term debt		$ 0				760
Make Whole Premium Additional Percent		0.15%	0.15%	0.15%
Senior Notes | INA Senior Notes Due March 2025 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount		$ 800
Long-term debt stated interest rate		3.15%	3.15%	3.15%
Short-term debt		$ 800				$ 0
Make Whole Premium Additional Percent		0.15%	0.15%	0.15%

[1] Redemption prices are equal to accrued and unpaid interest to the redemption date plus the greater of (i) 100 percent of the principal amount thereof, or (ii) sum of present value of scheduled payments of principal and interest on the capital securities from the redemption date to April 1, 2030.

[2] Refer to Note 1 g) to the Consolidated Financial Statements for additional information on the consolidation of VIEs.