INVESTMENTS - Fair Value of AFS Securities (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Debt securities AFS
Less than 12 months	$ 108,590	$ 60,316
12 months or longer	30,431	4,760
Total	139,021	65,076
Gross unrealized losses
Less than 12 months	869	267
12 months or longer	569	208
Total	1,438	475
Mortgage-backed securities - U.S. government-sponsored agency guaranteed
Debt securities AFS
Less than 12 months	10,965	3,588
12 months or longer	197	298
Total	11,162	3,886
Gross unrealized losses
Less than 12 months	182	30
12 months or longer	19	22
Total	201	52
Mortgage-backed securities - Non-U.S. residential
Debt securities AFS
Less than 12 months	58	1
12 months or longer	0	0
Total	58	1
Gross unrealized losses
Less than 12 months	0	0
12 months or longer	0	0
Total	0	0
Commercial
Debt securities AFS
Less than 12 months	2	7
12 months or longer	0	4
Total	2	11
Gross unrealized losses
Less than 12 months	0	0
12 months or longer	0	0
Total	0	0
Mortgage-backed securities
Debt securities AFS
Less than 12 months	11,025	3,596
12 months or longer	197	302
Total	11,222	3,898
Gross unrealized losses
Less than 12 months	182	30
12 months or longer	19	22
Total	201	52
U.S. Treasury
Debt securities AFS
Less than 12 months	38,146	25,031
12 months or longer	19,579	0
Total	57,725	25,031
Gross unrealized losses
Less than 12 months	122	49
12 months or longer	314	0
Total	436	49
Agency obligations
Debt securities AFS
Less than 12 months		50
12 months or longer		0
Total		50
Gross unrealized losses
Less than 12 months		0
12 months or longer		0
Total		0
U.S. Treasury and federal agency securities
Debt securities AFS
Less than 12 months		25,081
12 months or longer		0
Total		25,081
Gross unrealized losses
Less than 12 months		49
12 months or longer		0
Total		49
State and municipal
Debt securities AFS
Less than 12 months	198	836
12 months or longer	1,182	893
Total	1,380	1,729
Gross unrealized losses
Less than 12 months	5	34
12 months or longer	106	123
Total	111
Foreign government
Debt securities AFS
Less than 12 months	54,437	29,344
12 months or longer	9,452	3,502
Total	63,889	32,846
Gross unrealized losses
Less than 12 months	494	61
12 months or longer	130	61
Total	624	122
Corporate
Debt securities AFS
Less than 12 months	1,994	1,083
12 months or longer	21	24
Total	2,015	1,107
Gross unrealized losses
Less than 12 months	65	90
12 months or longer	0	1
Total	65	91
Asset-backed securities
Debt securities AFS
Less than 12 months	3	194
12 months or longer	0	39
Total	3	233
Gross unrealized losses
Less than 12 months	0	3
12 months or longer	0	1
Total	0	4
Other debt securities
Debt securities AFS
Less than 12 months	2,787	182
12 months or longer	0	0
Total	2,787	182
Gross unrealized losses
Less than 12 months	1	0
12 months or longer	0	0
Total	$ 1	$ 0