FAIR VALUE MEASUREMENTS - Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Assets
Gross derivatives	$ 950	$ 1,275
Netting adjustment	(512)	(821)
Derivative asset	437	454
Liabilities
Gross derivatives	671	1,241
Netting adjustment	(510)	(820)
Net derivative liabilities	161	420
Recurring
Assets
Investment securities	43,706	43,636
Netting adjustment	(512)	(821)
Derivative asset	437	454
Total assets	44,143	44,090
Liabilities
Netting adjustment	(510)	(820)
Net derivative liabilities	161	420
Other	428	379
Total liabilities	588	799
Recurring | Run-off insurance operations
Assets
Investment securities	37,592	35,503
Recurring | Level 1
Assets
Investment securities	4,767	6,732
Gross derivatives	0	0
Total assets	4,767	6,732
Liabilities
Gross derivatives	0	0
Other	0	0
Total liabilities	0	0
Recurring | Level 2
Assets
Investment securities	32,098	30,483
Gross derivatives	943	1,274
Total assets	33,042	31,757
Liabilities
Gross derivatives	669	1,240
Other	428	379
Total liabilities	1,097	1,619
Recurring | Level 3
Assets
Investment securities	6,841	6,421
Gross derivatives	6	1
Total assets	6,847	6,421
Liabilities
Gross derivatives	2	0
Other	0	0
Total liabilities	2	0
Recurring | Level 3 | U.S. corporate
Assets
Investment securities	3,873	3,548
Recurring | Level 3 | Mortgage and asset-backed
Assets
Investment securities	1,491	1,386
Recurring | Level 3 | Senior note | AerCap
Assets
Investment securities	$ 944	$ 900