Reinsurance - Rollforward of the reinsurable allowance for credit losses before adoption (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022	Jan. 01, 2021	Dec. 31, 2020
Fortitude RE
Effects of Reinsurance [Line Items]
Reinsurance assets, net of allowance for credit losses and disputes	$ 30,612	$ 30,751	$ 42,244	$ 36,801
Excluding Fortitude
Effects of Reinsurance [Line Items]
Reinsurance assets, net of allowance for credit losses and disputes	$ 36,914	38,971	39,432	36,300
As Previously Reported \| Fortitude RE
Effects of Reinsurance [Line Items]
Reinsurance assets, net of allowance for credit losses and disputes		32,159	34,578	29,135
As Previously Reported \| Excluding Fortitude
Effects of Reinsurance [Line Items]
Reinsurance assets, net of allowance for credit losses and disputes		$ 39,434	$ 38,963
Adjustments for NPR* > 100% \| Fortitude RE \| ASU 2018-12
Effects of Reinsurance [Line Items]
Reinsurance assets, net of allowance for credit losses and disputes				55
Change due to the current upper-medium grade discount rate \| Fortitude RE \| ASU 2018-12
Effects of Reinsurance [Line Items]
Reinsurance assets, net of allowance for credit losses and disputes				7,611
General Insurance
Effects of Reinsurance [Line Items]
Reinsurance assets, net of allowance for credit losses and disputes				5,400
Life and Retirement
Effects of Reinsurance [Line Items]
Reinsurance assets, net of allowance for credit losses and disputes				3,176
Life and Retirement \| As Previously Reported
Effects of Reinsurance [Line Items]
Reinsurance assets, net of allowance for credit losses and disputes				2,707
Life and Retirement \| Reclassification of cost of reinsurance \| ASU 2018-12
Effects of Reinsurance [Line Items]
Reinsurance assets, net of allowance for credit losses and disputes				416
Life and Retirement \| Reclassification to Market risk benefits \| ASU 2018-12
Effects of Reinsurance [Line Items]
Reinsurance assets, net of allowance for credit losses and disputes				(35)
Life and Retirement \| Adjustments for NPR* > 100% \| ASU 2018-12
Effects of Reinsurance [Line Items]
Reinsurance assets, net of allowance for credit losses and disputes				9
Life and Retirement \| Change due to the current upper-medium grade discount rate \| ASU 2018-12
Effects of Reinsurance [Line Items]
Reinsurance assets, net of allowance for credit losses and disputes				79
Life and Retirement \| Individual Retirement
Effects of Reinsurance [Line Items]
Reinsurance assets, net of allowance for credit losses and disputes				274
Life and Retirement \| Individual Retirement \| As Previously Reported
Effects of Reinsurance [Line Items]
Reinsurance assets, net of allowance for credit losses and disputes				309
Life and Retirement \| Individual Retirement \| Reclassification of cost of reinsurance \| ASU 2018-12
Effects of Reinsurance [Line Items]
Reinsurance assets, net of allowance for credit losses and disputes				0
Life and Retirement \| Individual Retirement \| Reclassification to Market risk benefits \| ASU 2018-12
Effects of Reinsurance [Line Items]
Reinsurance assets, net of allowance for credit losses and disputes				(35)
Life and Retirement \| Individual Retirement \| Adjustments for NPR* > 100% \| ASU 2018-12
Effects of Reinsurance [Line Items]
Reinsurance assets, net of allowance for credit losses and disputes				0
Life and Retirement \| Individual Retirement \| Change due to the current upper-medium grade discount rate \| ASU 2018-12
Effects of Reinsurance [Line Items]
Reinsurance assets, net of allowance for credit losses and disputes				0
Life and Retirement \| Life Insurance
Effects of Reinsurance [Line Items]
Reinsurance assets, net of allowance for credit losses and disputes				2,869
Life and Retirement \| Life Insurance \| As Previously Reported
Effects of Reinsurance [Line Items]
Reinsurance assets, net of allowance for credit losses and disputes				2,370
Life and Retirement \| Life Insurance \| Reclassification of cost of reinsurance \| ASU 2018-12
Effects of Reinsurance [Line Items]
Reinsurance assets, net of allowance for credit losses and disputes				416
Life and Retirement \| Life Insurance \| Reclassification to Market risk benefits \| ASU 2018-12
Effects of Reinsurance [Line Items]
Reinsurance assets, net of allowance for credit losses and disputes				0
Life and Retirement \| Life Insurance \| Adjustments for NPR* > 100% \| ASU 2018-12
Effects of Reinsurance [Line Items]
Reinsurance assets, net of allowance for credit losses and disputes				9
Life and Retirement \| Life Insurance \| Change due to the current upper-medium grade discount rate \| ASU 2018-12
Effects of Reinsurance [Line Items]
Reinsurance assets, net of allowance for credit losses and disputes				74
Life and Retirement \| Institutional Markets
Effects of Reinsurance [Line Items]
Reinsurance assets, net of allowance for credit losses and disputes				33
Life and Retirement \| Institutional Markets \| As Previously Reported
Effects of Reinsurance [Line Items]
Reinsurance assets, net of allowance for credit losses and disputes				28
Life and Retirement \| Institutional Markets \| Reclassification of cost of reinsurance \| ASU 2018-12
Effects of Reinsurance [Line Items]
Reinsurance assets, net of allowance for credit losses and disputes				0
Life and Retirement \| Institutional Markets \| Reclassification to Market risk benefits \| ASU 2018-12
Effects of Reinsurance [Line Items]
Reinsurance assets, net of allowance for credit losses and disputes				0
Life and Retirement \| Institutional Markets \| Adjustments for NPR* > 100% \| ASU 2018-12
Effects of Reinsurance [Line Items]
Reinsurance assets, net of allowance for credit losses and disputes				0
Life and Retirement \| Institutional Markets \| Change due to the current upper-medium grade discount rate \| ASU 2018-12
Effects of Reinsurance [Line Items]
Reinsurance assets, net of allowance for credit losses and disputes				$ 5