Debt (Schedule of Debt Outstanding) (Details) € in Millions, $ in Millions		Dec. 31, 2023 USD ($)	Dec. 31, 2023 EUR (€)	Dec. 31, 2022 USD ($)	Mar. 31, 2000 USD ($)
Debt Instrument [Line Items]
Repurchase agreements		$ 2,833		$ 1,419
Short-term debt		1,460		475
Long-term debt		13,035		14,402
Variable Interest Entity, Primary Beneficiary
Debt Instrument [Line Items]
Repurchase agreements		1,009		0
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%
Long-term debt		$ 0		699
Make Whole Premium Additional Percent		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%
Long-term debt		$ 0		742
Make Whole Premium Additional Percent		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%
Long-term debt		$ 799		798
Make Whole Premium Additional Percent		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%
Long-term debt		$ 1,497		1,496
Make Whole Premium Additional Percent		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%
Long-term debt		$ 623		609
Make Whole Premium Additional Percent		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%
Long-term debt		$ 974		952
Make Whole Premium Additional Percent		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%
Long-term debt		$ 758		740
Make Whole Premium Additional Percent		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%
Long-term debt		$ 994		993
Make Whole Premium Additional Percent		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%
Long-term debt		$ 621		606
Make Whole Premium Additional Percent		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%
Long-term debt		$ 298		298
Make Whole Premium Additional Percent		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%
Long-term debt		$ 918		927
Make Whole Premium Additional Percent		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%
Long-term debt		$ 971		949
Make Whole Premium Additional Percent		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%
Long-term debt		$ 718		726
Make Whole Premium Additional Percent		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%
Long-term debt		$ 471		471
Make Whole Premium Additional Percent		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%
Long-term debt		$ 1,486		1,485
Make Whole Premium Additional Percent		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%
Long-term debt		$ 593		593
Make Whole Premium Additional Percent		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%
Long-term debt		$ 984		984
Make Whole Premium Additional Percent		0.20%	0.20%
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%
Trust preferred securities	[1]	$ 308		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%
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%
Long-term debt		$ 230		$ 234
Make Whole Premium Additional Percent		0.25%	0.25%
Repurchase agreements
Debt Instrument [Line Items]
Weighted average interest rate on short-term debt		5.40%	5.40%	3.90%
Repurchase agreements		$ 1,824		$ 1,419
Repurchase agreements | Variable Interest Entity, Primary Beneficiary
Debt Instrument [Line Items]
Weighted average interest rate on short-term debt		4.90%	4.90%
Repurchase agreements	[2]	$ 1,009		0
Senior Notes | INA Senior Notes Due March 2023 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount		$ 475
Long-term debt stated interest rate		2.70%	2.70%
Short-term debt		$ 0		475
Make Whole Premium Additional Percent		0.10%	0.10%
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%
Short-term debt		$ 700		0
Make Whole Premium Additional Percent		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%
Short-term debt		$ 760		$ 0
Make Whole Premium Additional Percent		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.