INVESTMENTS - Fair Value of AFS Securities (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Debt securities AFS
Less than 12 months	$ 66,277	$ 96,451
12 months or longer	3,274	41,434
Total	69,551	137,885
Gross unrealized losses
Less than 12 months	421	802
12 months or longer	80	311
Total	501	1,113
Mortgage-backed securities - U.S. government-sponsored agency guaranteed
Debt securities AFS
Less than 12 months	6,833	9,780
12 months or longer	318	1,877
Total	7,151	11,657
Gross unrealized losses
Less than 12 months	67	242
12 months or longer	22	38
Total	89	280
Mortgage-backed securities - Non-U.S. residential
Debt securities AFS
Less than 12 months	4	208
12 months or longer	0	1
Total	4	209
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	10	16
12 months or longer	5	27
Total	15	43
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	6,847	10,004
12 months or longer	323	1,905
Total	7,170	11,909
Gross unrealized losses
Less than 12 months	67	242
12 months or longer	22	38
Total	89	280
U.S. Treasury
Debt securities AFS
Less than 12 months		45,484
12 months or longer		26,907
Total		72,391
Gross unrealized losses
Less than 12 months		248
12 months or longer		132
Total		380
Agency obligations
Debt securities AFS
Less than 12 months		781
12 months or longer		3,897
Total		4,678
Gross unrealized losses
Less than 12 months		2
12 months or longer		18
Total		20
U.S. Treasury and federal agency securities
Debt securities AFS
Less than 12 months	24,817	46,265
12 months or longer	0	30,804
Total	24,817	77,069
Gross unrealized losses
Less than 12 months	12	250
12 months or longer	0	150
Total	12	400
State and municipal
Debt securities AFS
Less than 12 months	3,302	362
12 months or longer	24	266
Total	3,326	628
Gross unrealized losses
Less than 12 months	100	62
12 months or longer	1	27
Total	101	89
Foreign government
Debt securities AFS
Less than 12 months	28,879	35,485
12 months or longer	2,902	8,170
Total	31,781	43,655
Gross unrealized losses
Less than 12 months	144	149
12 months or longer	55	92
Total	199	241
Corporate
Debt securities AFS
Less than 12 months	1,836	2,916
12 months or longer	24	123
Total	1,860	3,039
Gross unrealized losses
Less than 12 months	92	98
12 months or longer	2	3
Total	94	101
Asset-backed securities
Debt securities AFS
Less than 12 months	240	112
12 months or longer	1	166
Total	241	278
Gross unrealized losses
Less than 12 months	6	1
12 months or longer	0	1
Total	6	2
Other debt securities
Debt securities AFS
Less than 12 months	356	1,307
12 months or longer	0	0
Total	356	1,307
Gross unrealized losses
Less than 12 months	0	0
12 months or longer	0	0
Total	$ 0	$ 0