INVESTMENTS - Fair Value of AFS Securities (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Fair value
Less than 12 months	$ 68,298	$ 138,567
12 months or longer	98,800	53,695
Total	167,098	192,262
Gross unrealized losses
Less than 12 months	861	3,997
12 months or longer	2,933	2,607
Total	3,794	6,604
U.S. government-sponsored agency guaranteed
Fair value
Less than 12 months	8,602	7,908
12 months or longer	9,734	3,290
Total	18,336	11,198
Gross unrealized losses
Less than 12 months	86	412
12 months or longer	648	343
Total	734	755
Residential
Fair value
Less than 12 months	352	158
12 months or longer	34	1
Total	386	159
Gross unrealized losses
Less than 12 months	1	3
12 months or longer	2	0
Total	3	3
Commercial
Fair value
Less than 12 months	0	1
12 months or longer	0	1
Total	0	2
Gross unrealized losses
Less than 12 months	0	0
12 months or longer	0	0
Total	0	0
Mortgage-backed securities
Fair value
Less than 12 months	8,954	8,067
12 months or longer	9,768	3,292
Total	18,722	11,359
Gross unrealized losses
Less than 12 months	87	415
12 months or longer	650	343
Total	737	758
U.S. Treasury
Fair value
Less than 12 months	11,851	40,701
12 months or longer	57,669	34,692
Total	69,520	75,393
Gross unrealized losses
Less than 12 months	113	1,001
12 months or longer	1,269	1,491
Total	1,382	2,492
U.S. Treasury and federal agency securities
Fair value
Less than 12 months	11,851	40,701
12 months or longer	57,669	34,692
Total	69,520	75,393
Gross unrealized losses
Less than 12 months	113	1,001
12 months or longer	1,269	1,491
Total	1,382	2,492
State and municipal
Fair value
Less than 12 months	906	896
12 months or longer	324	707
Total	1,230	1,603
Gross unrealized losses
Less than 12 months	17	31
12 months or longer	74	128
Total	91	159
Foreign government
Fair value
Less than 12 months	42,250	82,900
12 months or longer	29,176	14,220
Total	71,426	97,120
Gross unrealized losses
Less than 12 months	540	2,332
12 months or longer	835	608
Total	1,375	2,940
Corporate
Fair value
Less than 12 months	2,319	3,082
12 months or longer	1,619	784
Total	3,938	3,866
Gross unrealized losses
Less than 12 months	103	209
12 months or longer	105	37
Total	208	246
Asset-backed securities
Fair value
Less than 12 months	154	708
12 months or longer	16	0
Total	170	708
Gross unrealized losses
Less than 12 months	0	4
12 months or longer	0	0
Total	0	4
Other debt securities
Fair value
Less than 12 months	1,864	2,213
12 months or longer	228	0
Total	2,092	2,213
Gross unrealized losses
Less than 12 months	1	5
12 months or longer	0	0
Total	$ 1	$ 5