INVESTMENTS - Fair Value of AFS Securities (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Fair value
Less than 12 months	$ 109,320	$ 138,567
12 months or longer	79,897	53,695
Total	189,217	192,262
Gross unrealized losses
Less than 12 months	2,543	3,997
12 months or longer	2,734	2,607
Total	5,277	6,604
Mortgage-backed securities - U.S. government-sponsored agency guaranteed
Fair value
Less than 12 months	7,751	7,908
12 months or longer	8,945	3,290
Total	16,696	11,198
Gross unrealized losses
Less than 12 months	154	412
12 months or longer	804	343
Total	958	755
Residential mortgages
Fair value
Less than 12 months	298	158
12 months or longer	4	1
Total	302	159
Gross unrealized losses
Less than 12 months	3	3
12 months or longer	0	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	8,049	8,067
12 months or longer	8,949	3,292
Total	16,998	11,359
Gross unrealized losses
Less than 12 months	157	415
12 months or longer	804	343
Total	961	758
U.S. Treasury
Fair value
Less than 12 months	23,045	40,701
12 months or longer	48,721	34,692
Total	71,766	75,393
Gross unrealized losses
Less than 12 months	705	1,001
12 months or longer	1,077	1,491
Total	1,782	2,492
Agency obligations
Fair value
Less than 12 months		0
12 months or longer		0
Total		0
Gross unrealized losses
Less than 12 months		0
12 months or longer		0
Total		0
U.S. Treasury and federal agency securities
Fair value
Less than 12 months	23,045	40,701
12 months or longer	48,721	34,692
Total	71,766	75,393
Gross unrealized losses
Less than 12 months	705	1,001
12 months or longer	1,077	1,491
Total	1,782	2,492
State and municipal
Fair value
Less than 12 months	751	896
12 months or longer	864	707
Total	1,615	1,603
Gross unrealized losses
Less than 12 months	39	31
12 months or longer	140	128
Total	179	159
Foreign government
Fair value
Less than 12 months	73,044	82,900
12 months or longer	19,780	14,220
Total	92,824	97,120
Gross unrealized losses
Less than 12 months	1,425	2,332
12 months or longer	658	608
Total	2,083	2,940
Corporate
Fair value
Less than 12 months	2,858	3,082
12 months or longer	1,583	784
Total	4,441	3,866
Gross unrealized losses
Less than 12 months	213	209
12 months or longer	55	37
Total	268	246
Asset-backed securities
Fair value
Less than 12 months	214	708
12 months or longer	0	0
Total	214	708
Gross unrealized losses
Less than 12 months	2	4
12 months or longer	0	0
Total	2	4
Other debt securities
Fair value
Less than 12 months	1,359	2,213
12 months or longer	0	0
Total	1,359	2,213
Gross unrealized losses
Less than 12 months	2	5
12 months or longer	0	0
Total	$ 2	$ 5