INVESTMENTS - Fair Value of AFS Debt Securities by Contractual Maturity Date (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Amoritzed cost
Amortized cost	$ 273,378	$ 290,423
Fair value
Total fair value	273,435	288,038
Mortgage-backed securities
Amoritzed cost
Amortized cost, due within 1 year	12	14
Amortized cost, after 1 but within 5 years	589	662
Amortized cost, after 5 but within 10 years	1,986	2,779
Amortized cost, after 10 years	35,923	41,533
Amortized cost	38,510	44,988
Fair value
Fair value, due within 1 year	12	14
Fair value, after 1 but within 5 years	590	661
Fair value, after 5 but within 10 years	2,133	2,828
Fair value, after 10 years	36,150	41,002
Total fair value	38,885	44,505
U.S. Treasury and federal agency securities
Amoritzed cost
Amortized cost, due within 1 year	42,893	41,941
Amortized cost, after 1 but within 5 years	66,636	76,139
Amortized cost, after 5 but within 10 years	497	489
Amortized cost, after 10 years	25	90
Amortized cost	110,051	118,659
Fair value
Fair value, due within 1 year	42,803	41,867
Fair value, after 1 but within 5 years	66,189	74,800
Fair value, after 5 but within 10 years	489	462
Fair value, after 10 years	28	93
Total fair value	109,509	117,222
State and municipal securities
Amoritzed cost
Amortized cost, due within 1 year	1,282	2,586
Amortized cost, after 1 but within 5 years	1,188	1,676
Amortized cost, after 5 but within 10 years	446	585
Amortized cost, after 10 years	3,312	4,525
Amortized cost	6,228	9,372
Fair value
Fair value, due within 1 year	1,251	2,586
Fair value, after 1 but within 5 years	1,165	1,675
Fair value, after 5 but within 10 years	454	602
Fair value, after 10 years	3,300	4,343
Total fair value	6,170	9,206
Foreign government
Amoritzed cost
Amortized cost, due within 1 year	41,222	39,078
Amortized cost, after 1 but within 5 years	49,183	50,125
Amortized cost, after 5 but within 10 years	9,758	10,153
Amortized cost, after 10 years	1,237	1,516
Amortized cost	101,400	100,872
Fair value
Fair value, due within 1 year	41,247	39,028
Fair value, after 1 but within 5 years	49,472	49,962
Fair value, after 5 but within 10 years	9,836	10,149
Fair value, after 10 years	1,185	1,552
Total fair value	101,740	100,691
All other
Amoritzed cost
Amortized cost, due within 1 year	7,424	6,166
Amortized cost, after 1 but within 5 years	8,297	8,459
Amortized cost, after 5 but within 10 years	1,249	1,474
Amortized cost, after 10 years	219	433
Amortized cost	17,189	16,532
Fair value
Fair value, due within 1 year	7,420	6,166
Fair value, after 1 but within 5 years	8,306	8,416
Fair value, after 5 but within 10 years	1,213	1,427
Fair value, after 10 years	192	405
Total fair value	$ 17,131	$ 16,414

Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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