INVESTMENTS - Carrying Value and Fair Value of HTM Debt Securities by Contractual Maturity Dates (Details) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Held-to-maturity Securities, Debt Maturities, Net Carrying Amount;
Carrying value	$ 50,175	$ 45,667
Held-to-maturity Securities, Debt Maturities, Fair Value;
Fair value	50,523	45,555
Mortgage-backed securities
Held-to-maturity Securities, Debt Maturities, Net Carrying Amount;
Due within 1 year, carrying value	0	0
After 1 but within 5 years, carrying value	735	760
After 5 but within 10 years, carrying value	51	54
After 10 years, carrying value	25,556	23,830
Carrying value	26,342	24,644
Held-to-maturity Securities, Debt Maturities, Fair Value;
Due within 1 year, fair value	0	0
After 1 but within 5 years, fair value	743	766
After 5 but within 10 years, fair value	52	55
After 10 years, fair value	25,671	23,810
Fair value	26,466	24,631
State and municipal securities
Held-to-maturity Securities, Debt Maturities, Net Carrying Amount;
Due within 1 year, carrying value	463	406
After 1 but within 5 years, carrying value	145	112
After 5 but within 10 years, carrying value	372	363
After 10 years, carrying value	7,819	7,702
Carrying value	8,799	8,583
Held-to-maturity Securities, Debt Maturities, Fair Value;
Due within 1 year, fair value	472	406
After 1 but within 5 years, fair value	152	110
After 5 but within 10 years, fair value	385	367
After 10 years, fair value	7,968	7,591
Fair value	8,977	8,474
Foreign government
Held-to-maturity Securities, Debt Maturities, Net Carrying Amount;
Due within 1 year, carrying value	138	824
After 1 but within 5 years, carrying value	450	515
After 5 but within 10 years, carrying value	0	0
After 10 years, carrying value	0	0
Carrying value	588	1,339
Held-to-maturity Securities, Debt Maturities, Fair Value;
Due within 1 year, fair value	138	818
After 1 but within 5 years, fair value	434	495
After 5 but within 10 years, fair value	0	0
After 10 years, fair value	0	0
Fair value	572	1,313
All other
Held-to-maturity Securities, Debt Maturities, Net Carrying Amount;
Due within 1 year, carrying value	0	0
After 1 but within 5 years, carrying value	0	0
After 5 but within 10 years, carrying value	468	513
After 10 years, carrying value	13,978	10,588
Carrying value	14,446	11,101
Held-to-maturity Securities, Debt Maturities, Fair Value;
Due within 1 year, fair value	0	0
After 1 but within 5 years, fair value	0	0
After 5 but within 10 years, fair value	469	514
After 10 years, fair value	14,039	10,623
Fair value	$ 14,508	$ 11,137

Amount after other than temporary impairment (OTTI) accretion, of investments in debt securities classified as held-to-maturity.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 5
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Fair value of held-to-maturity debt securities maturing in the sixth fiscal year through the tenth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Carrying amount of debt securities accounted for as held-to-maturity, net of adjustments including, but not limited to, accretion, amortization, collection of cash, previous other-than-temporary impairments (OTTI) recognized, and fair value hedge accounting adjustments, maturing in the fifth through tenth fiscal year following the latest fiscal year.

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Fair value of held-to-maturity debt securities maturing in the second fiscal year through the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Fair value of held-to-maturity debt securities maturing after the tenth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Carrying amount of debt securities accounted for as held-to-maturity, net of adjustments including, but not limited to, accretion, amortization, collection of cash, previous other-than-temporary impairments (OTTI) recognized, and fair value hedge accounting adjustments, maturing after the tenth fiscal year following the latest fiscal year.

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Fair value of held-to-maturity debt securities maturing in the next fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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