INVESTMENTS - Debt Securities Held-to-Maturity (Details) - USD ($) $ in Millions	3 Months Ended
	Jun. 30, 2015	Mar. 31, 2016	Dec. 31, 2015
Debt Securities Held-to-maturity
Amortized cost basis		$ 37,304	$ 36,668
Net unrealized gains (losses) recognized in AOCI		(414)	(453)
Carrying value		36,890	36,215
Gross unrealized gains		878	690
Gross unrealized (losses)		(318)	(394)
Fair value		37,450	36,511
Fair value of securities transferred from AFS to HTM	$ 7,100
Mortgage-backed securities - U.S. agency-sponsored
Debt Securities Held-to-maturity
Amortized cost basis		17,771	17,648
Net unrealized gains (losses) recognized in AOCI		134	138
Carrying value		17,905	17,786
Gross unrealized gains		264	71
Gross unrealized (losses)		(2)	(100)
Fair value		18,167	17,757
Fair value of securities transferred from AFS to HTM	7,000
Mortgage-backed securities - Prime
Debt Securities Held-to-maturity
Amortized cost basis		51	121
Net unrealized gains (losses) recognized in AOCI		(10)	(78)
Carrying value		41	43
Gross unrealized gains		3	3
Gross unrealized (losses)		(2)	(1)
Fair value		42	45
Mortgage-backed securities - Alt-A
Debt Securities Held-to-maturity
Amortized cost basis		427	433
Net unrealized gains (losses) recognized in AOCI		(51)	(1)
Carrying value		376	432
Gross unrealized gains		228	259
Gross unrealized (losses)		(157)	(162)
Fair value		447	529
Mortgage-backed securities - Subprime
Debt Securities Held-to-maturity
Amortized cost basis		2	2
Net unrealized gains (losses) recognized in AOCI		0	0
Carrying value		2	2
Gross unrealized gains		11	13
Gross unrealized (losses)		0	0
Fair value		13	15
Mortgage-backed securities - Non-U.S. residential
Debt Securities Held-to-maturity
Amortized cost basis		1,290	1,330
Net unrealized gains (losses) recognized in AOCI		(58)	(60)
Carrying value		1,232	1,270
Gross unrealized gains		35	37
Gross unrealized (losses)		0	0
Fair value		1,267	1,307
Mortgage-backed securities
Debt Securities Held-to-maturity
Amortized cost basis		19,541	19,534
Net unrealized gains (losses) recognized in AOCI		15	(1)
Carrying value		19,556	19,533
Gross unrealized gains		541	383
Gross unrealized (losses)		(161)	(263)
Fair value		19,936	19,653
State and municipal securities
Debt Securities Held-to-maturity
Amortized cost basis		8,521	8,581
Net unrealized gains (losses) recognized in AOCI		(421)	(438)
Carrying value		8,100	8,143
Gross unrealized gains		309	245
Gross unrealized (losses)		(85)	(87)
Fair value		8,324	8,301
Fair value of securities transferred from AFS to HTM	$ 100
Foreign government
Debt Securities Held-to-maturity
Amortized cost basis		4,057	4,068
Net unrealized gains (losses) recognized in AOCI		0	0
Carrying value		4,057	4,068
Gross unrealized gains		14	28
Gross unrealized (losses)		0	(3)
Fair value		4,071	4,093
Asset-backed securities
Debt Securities Held-to-maturity
Amortized cost basis		5,185	4,485
Net unrealized gains (losses) recognized in AOCI		(8)	(14)
Carrying value		5,177	4,471
Gross unrealized gains		14	34
Gross unrealized (losses)		(72)	(41)
Fair value		$ 5,119	$ 4,464