INVESTMENTS - Fair Value of AFS Securities (Details) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Debt securities AFS
Less than 12 months	$ 65,280	$ 96,451
12 months or longer	3,587	41,434
Total	68,867	137,885
Gross unrealized losses
Less than 12 months	551	802
12 months or longer	108	311
Total	659	1,113
Mortgage-backed securities - U.S. government-sponsored agency guaranteed
Debt securities AFS
Less than 12 months	8,915	9,780
12 months or longer	551	1,877
Total	9,466	11,657
Gross unrealized losses
Less than 12 months	183	242
12 months or longer	22	38
Total	205	280
Mortgage-backed securities - Non-U.S. residential
Debt securities AFS
Less than 12 months	129	208
12 months or longer	0	1
Total	129	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	12	16
12 months or longer	5	27
Total	17	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	9,056	10,004
12 months or longer	556	1,905
Total	9,612	11,909
Gross unrealized losses
Less than 12 months	183	242
12 months or longer	22	38
Total	205	280
U.S. Treasury
Debt securities AFS
Less than 12 months	27,202	45,484
12 months or longer	0	26,907
Total	27,202	72,391
Gross unrealized losses
Less than 12 months	2	248
12 months or longer	0	132
Total	2	380
Agency obligations
Debt securities AFS
Less than 12 months	0	781
12 months or longer	250	3,897
Total	250	4,678
Gross unrealized losses
Less than 12 months	0	2
12 months or longer	0	18
Total	0	20
U.S. Treasury and federal agency securities
Debt securities AFS
Less than 12 months	27,202	46,265
12 months or longer	250	30,804
Total	27,452	77,069
Gross unrealized losses
Less than 12 months	2	250
12 months or longer	0	150
Total	2	400
State and municipal
Debt securities AFS
Less than 12 months	4,607	362
12 months or longer	234	266
Total	4,841	628
Gross unrealized losses
Less than 12 months	109	62
12 months or longer	22	27
Total	131	89
Foreign government
Debt securities AFS
Less than 12 months	22,236	35,485
12 months or longer	2,519	8,170
Total	24,755	43,655
Gross unrealized losses
Less than 12 months	121	149
12 months or longer	61	92
Total	182	241
Corporate
Debt securities AFS
Less than 12 months	1,599	2,916
12 months or longer	27	123
Total	1,626	3,039
Gross unrealized losses
Less than 12 months	129	98
12 months or longer	3	3
Total	132	101
Asset-backed securities
Debt securities AFS
Less than 12 months	239	112
12 months or longer	1	166
Total	240	278
Gross unrealized losses
Less than 12 months	7	1
12 months or longer	0	1
Total	7	2
Other debt securities
Debt securities AFS
Less than 12 months	341	1,307
12 months or longer	0	0
Total	341	1,307
Gross unrealized losses
Less than 12 months	0	0
12 months or longer	0	0
Total	$ 0	$ 0