INVESTMENTS - Debt Securities Held-to-Maturity (Details) - USD ($) $ in Millions	3 Months Ended
Dec. 31, 2016	Jun. 30, 2017
Debt Securities Held-to-maturity
Amortized cost basis	$ 46,163	$ 50,251
Net unrealized gains (losses) recognized in AOCI	(496)	(76)
Carrying value	45,667	50,175
Gross unrealized gains	345	615
Gross unrealized (losses)	(457)	(267)
Fair value	45,555	50,523
Fair value of AFS securities transferred to HTM	5,800
Mortgage-backed securities - U.S. agency-sponsored
Debt Securities Held-to-maturity
Amortized cost basis	22,462	24,044
Net unrealized gains (losses) recognized in AOCI	33	25
Carrying value	22,495	24,069
Gross unrealized gains	47	77
Gross unrealized (losses)	(186)	(113)
Fair value	22,356	24,033
Fair value of AFS securities transferred to HTM	5,000
Mortgage-backed securities - Prime
Debt Securities Held-to-maturity
Amortized cost basis	31	15
Net unrealized gains (losses) recognized in AOCI	(7)	0
Carrying value	24	15
Gross unrealized gains	10	3
Gross unrealized (losses)	(1)	0
Fair value	33	18
Mortgage-backed securities - Alt-A
Debt Securities Held-to-maturity
Amortized cost basis	314	279
Net unrealized gains (losses) recognized in AOCI	(27)	(18)
Carrying value	287	261
Gross unrealized gains	69	94
Gross unrealized (losses)	(1)	(1)
Fair value	355	354
Mortgage-backed securities - Non-U.S. residential
Debt Securities Held-to-maturity
Amortized cost basis	1,871	1,940
Net unrealized gains (losses) recognized in AOCI	(47)	(47)
Carrying value	1,824	1,893
Gross unrealized gains	49	64
Gross unrealized (losses)	0	0
Fair value	1,873	1,957
Mortgage-backed securities - Commercial
Debt Securities Held-to-maturity
Amortized cost basis	14	104
Net unrealized gains (losses) recognized in AOCI	0	0
Carrying value	14	104
Gross unrealized gains	0	0
Gross unrealized (losses)	0	0
Fair value	14	104
Mortgage-backed securities
Debt Securities Held-to-maturity
Amortized cost basis	24,692	26,382
Net unrealized gains (losses) recognized in AOCI	(48)	(40)
Carrying value	24,644	26,342
Gross unrealized gains	175	238
Gross unrealized (losses)	(188)	(114)
Fair value	24,631	26,466
State and municipal securities
Debt Securities Held-to-maturity
Amortized cost basis	9,025	8,830
Net unrealized gains (losses) recognized in AOCI	(442)	(31)
Carrying value	8,583	8,799
Gross unrealized gains	129	310
Gross unrealized (losses)	(238)	(132)
Fair value	8,474	8,977
Fair value of AFS securities transferred to HTM	830
Foreign government
Debt Securities Held-to-maturity
Amortized cost basis	1,339	588
Net unrealized gains (losses) recognized in AOCI	0	0
Carrying value	1,339	588
Gross unrealized gains	0	0
Gross unrealized (losses)	(26)	(16)
Fair value	1,313	572
Asset-backed securities
Debt Securities Held-to-maturity
Amortized cost basis	11,107	14,451
Net unrealized gains (losses) recognized in AOCI	(6)	(5)
Carrying value	11,101	14,446
Gross unrealized gains	41	67
Gross unrealized (losses)	(5)	(5)
Fair value	$ 11,137	$ 14,508

Available for Sale Securities, Transfers to Held-to-Maturity Securities, Fair Value

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Held to Maturity Securities Accumulated Unrecognized Gain (Loss) Including Other than Temporary Impairment Not Credit Loss Pre Tax

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

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
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-Section 50
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Amount of accumulated unrealized loss on investments in debt securities classified as held-to-maturity.

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

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Fair value of investments in debt securities classified as held-to-maturity.

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