INVESTMENTS - Fair Value of AFS Securities (Details) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Fair value
Less than 12 months	$ 116,954	$ 122,278
12 months or longer	21,493	22,358
Total	138,447	144,636
Gross unrealized losses
Less than 12 months	926	1,394
12 months or longer	716	1,172
Total	1,642	2,566
Mortgage-backed securities - U.S. agency-sponsored
Fair value
Less than 12 months	26,236	23,534
12 months or longer	2,253	2,236
Total	28,489	25,770
Gross unrealized losses
Less than 12 months	332	436
12 months or longer	67	70
Total	399	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	1,243	486
12 months or longer	36	1,276
Total	1,279	1,762
Gross unrealized losses
Less than 12 months	4	0
12 months or longer	1	7
Total	5	7
Mortgage-backed securities - Commercial
Fair value
Less than 12 months	84	75
12 months or longer	37	58
Total	121	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	27,563	24,096
12 months or longer	2,326	3,570
Total	29,889	27,666
Gross unrealized losses
Less than 12 months	337	437
12 months or longer	68	77
Total	405	514
U.S. Treasury
Fair value
Less than 12 months	37,721	44,342
12 months or longer	4,592	1,335
Total	42,313	45,677
Gross unrealized losses
Less than 12 months	250	445
12 months or longer	109	7
Total	359	452
Agency obligations
Fair value
Less than 12 months	6,345	6,552
12 months or longer	106	250
Total	6,451	6,802
Gross unrealized losses
Less than 12 months	60	83
12 months or longer	1	2
Total	61	85
U.S. Treasury and federal agency securities
Fair value
Less than 12 months	44,066	50,894
12 months or longer	4,698	1,585
Total	48,764	52,479
Gross unrealized losses
Less than 12 months	310	528
12 months or longer	110	9
Total	420	537
State and municipal securities
Fair value
Less than 12 months	506	1,616
12 months or longer	1,735	3,116
Total	2,241	4,732
Gross unrealized losses
Less than 12 months	17	55
12 months or longer	286	702
Total	303	757
Foreign government
Fair value
Less than 12 months	37,764	38,226
12 months or longer	11,189	8,973
Total	48,953	47,199
Gross unrealized losses
Less than 12 months	172	243
12 months or longer	229	311
Total	401	554
Corporate
Fair value
Less than 12 months	5,965	7,011
12 months or longer	553	1,877
Total	6,518	8,888
Gross unrealized losses
Less than 12 months	87	129
12 months or longer	14	47
Total	101	176
Asset-backed securities
Fair value
Less than 12 months	1,045	411
12 months or longer	938	3,213
Total	1,983	3,624
Gross unrealized losses
Less than 12 months	1	0
12 months or longer	5	22
Total	6	22
Other
Fair value
Less than 12 months	29	5
12 months or longer	0	0
Total	29	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	16	19
12 months or longer	54	24
Total	70	43
Gross unrealized losses
Less than 12 months	2	2
12 months or longer	4	4
Total	$ 6	$ 6