Segment Information - Schedule of Continuing Operations by Operating Segment (Details) $ in Millions	3 Months Ended
	Mar. 31, 2026 USD ($) segment	Mar. 31, 2025 USD ($)
Segment Reporting Information [Line Items]
Net Premiums Earned	$ 6,072	$ 5,770
Loss and Loss Adjustment Expenses Incurred	3,475	3,794
Amortization of DAC	824	825
General Operating Expense	1,137	1,115
Net Investment Income	712	1,105
Income before income tax expense	987	960
Interest expense	100	92
Changes in the fair values of equity securities, AIG's investment in Corebridge and gain/loss on sale of shares	(237)	217
Other income (expense) - net	2
Realized gains (losses)	(135)	(103)
Net realized gains (losses), net investment income	0	(2)
Net realized gains (losses), reconciliation to income (loss) from continuing operations before income tax expense	(136)	(66)
Net gain (loss) on divestitures and other	(127)	3
Non-operating litigation reserves and settlements		11
(Unfavorable) favorable prior year development and related amortization changes ceded under retroactive reinsurance agreements	8	(9)
Net loss reserve discount benefit (charge)	48	(17)
Net results of businesses in run-off	9	5
Net results of businesses in run-off, net investment income, reconciliation to income (loss) from continuing operations before income tax expense	(5)	5
Non-operating pension expenses	1	(5)
Integration and transaction costs associated with acquiring or divesting businesses	(7)	(5)
Restructuring and other costs	$ (76)	$ (76)
Restructuring Charges, Statement of Income or Comprehensive Income [Extensible Enumeration]	General Operating Expense	General Operating Expense
Non-recurring costs related to regulatory or accounting changes	$ (5)	$ (4)
Number of reportable segments | segment	3
Fortitude Re funds withheld assets
Segment Reporting Information [Line Items]
Net Investment Income	$ 23	40
Realized gains (losses)	(13)	(2)
Fortitude Re funds withheld embedded derivative
Segment Reporting Information [Line Items]
Realized gains (losses)	10	(41)
Total
Segment Reporting Information [Line Items]
Net Investment Income	915	845
Income before income tax expense	1,503	909
Reportable Segments
Segment Reporting Information [Line Items]
Net Premiums Written	5,599	4,526
Net Premiums Earned	6,052	5,769
Loss and Loss Adjustment Expenses Incurred	3,509	3,766
Amortization of DAC	818	825
Other Acquisition Expenses	233	232
General Operating Expense	718	703
Underwriting Income (Loss)	774	243
Net Investment Income	864	736
Income before income tax expense	1,628	975
Interest expense	(100)	(91)
Amortization of intangible assets and renewal rights	(10)	(4)
Other Operations
Segment Reporting Information [Line Items]
Net Investment Income	52	108
Income before income tax expense	(25)	25
Elimination and consolidations
Segment Reporting Information [Line Items]
Net Investment Income	(1)	1
Income before income tax expense	0	0
North America Commercial | Reportable Segments
Segment Reporting Information [Line Items]
Net Premiums Written	1,605	1,174
Net Premiums Earned	2,253	2,124
Loss and Loss Adjustment Expenses Incurred	1,421	1,526
Amortization of DAC	213	227
Other Acquisition Expenses	68	47
General Operating Expense	224	195
Underwriting Income (Loss)	327	129
International Commercial | Reportable Segments
Segment Reporting Information [Line Items]
Net Premiums Written	2,450	2,027
Net Premiums Earned	2,187	2,051
Loss and Loss Adjustment Expenses Incurred	1,246	1,178
Amortization of DAC	278	245
Other Acquisition Expenses	85	94
General Operating Expense	300	294
Underwriting Income (Loss)	278	240
Global Personal | Reportable Segments
Segment Reporting Information [Line Items]
Net Premiums Written	1,544	1,325
Net Premiums Earned	1,612	1,594
Loss and Loss Adjustment Expenses Incurred	842	1,062
Amortization of DAC	327	353
Other Acquisition Expenses	80	91
General Operating Expense	194	214
Underwriting Income (Loss)	$ 169	$ (126)