INVESTMENTS - Fair Value of AFS Securities (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Fair value
Less than 12 months	$ 107,721	$ 122,278
12 months or longer	20,818	22,358
Total	128,539	144,636
Gross unrealized losses
Less than 12 months	1,202	1,394
12 months or longer	1,049	1,172
Total	2,251	2,566
Mortgage-backed securities - U.S. agency-sponsored
Fair value
Less than 12 months	21,496	23,534
12 months or longer	2,043	2,236
Total	23,539	25,770
Gross unrealized losses
Less than 12 months	423	436
12 months or longer	66	70
Total	489	506
Mortgage-backed securities - Prime
Fair value
Less than 12 months		1
12 months or longer		0
Total		1
Gross unrealized losses
Less than 12 months		0
12 months or longer		0
Total		0
Mortgage-backed securities - Non-U.S. residential
Fair value
Less than 12 months	423	486
12 months or longer	803	1,276
Total	1,226	1,762
Gross unrealized losses
Less than 12 months	1	0
12 months or longer	21	7
Total	22	7
Mortgage-backed securities - Commercial
Fair value
Less than 12 months	91	75
12 months or longer	49	58
Total	140	133
Gross unrealized losses
Less than 12 months	1	1
12 months or longer	0	0
Total	1	1
Mortgage-backed securities
Fair value
Less than 12 months	22,010	24,096
12 months or longer	2,895	3,570
Total	24,905	27,666
Gross unrealized losses
Less than 12 months	425	437
12 months or longer	87	77
Total	512	514
U.S. Treasury
Fair value
Less than 12 months	38,221	44,342
12 months or longer	955	1,335
Total	39,176	45,677
Gross unrealized losses
Less than 12 months	393	445
12 months or longer	3	7
Total	396	452
Agency obligations
Fair value
Less than 12 months	6,099	6,552
12 months or longer	145	250
Total	6,244	6,802
Gross unrealized losses
Less than 12 months	70	83
12 months or longer	0	2
Total	70	85
U.S. Treasury and federal agency securities
Fair value
Less than 12 months	44,320	50,894
12 months or longer	1,100	1,585
Total	45,420	52,479
Gross unrealized losses
Less than 12 months	463	528
12 months or longer	3	9
Total	466	537
State and municipal securities
Fair value
Less than 12 months	1,039	1,616
12 months or longer	2,883	3,116
Total	3,922	4,732
Gross unrealized losses
Less than 12 months	47	55
12 months or longer	637	702
Total	684	757
Foreign government
Fair value
Less than 12 months	33,770	38,226
12 months or longer	11,624	8,973
Total	45,394	47,199
Gross unrealized losses
Less than 12 months	173	243
12 months or longer	294	311
Total	467	554
Corporate
Fair value
Less than 12 months	6,278	7,011
12 months or longer	881	1,877
Total	7,159	8,888
Gross unrealized losses
Less than 12 months	93	129
12 months or longer	16	47
Total	109	176
Asset-backed securities
Fair value
Less than 12 months	221	411
12 months or longer	1,369	3,213
Total	1,590	3,624
Gross unrealized losses
Less than 12 months	0	0
12 months or longer	8	22
Total	8	22
Other
Fair value
Less than 12 months	70	5
12 months or longer	0	0
Total	70	5
Gross unrealized losses
Less than 12 months	0	0
12 months or longer	0	0
Total	0	0
Equity securities
Fair value
Less than 12 months	13	19
12 months or longer	66	24
Total	79	43
Gross unrealized losses
Less than 12 months	1	2
12 months or longer	4	4
Total	$ 5	$ 6