CHANGES IN ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) - Change in Each Component of AOCI (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016	Dec. 31, 2015
Change in accumulated other comprehensive income (loss)
Balance, beginning of period		$ 226,143
Balance, end of period		229,153	$ 228,761
Net unrealized gains (losses) on investment securities
Change in accumulated other comprehensive income (loss)
Balance, beginning of period		(799)	(907)
Adjustment to opening balance, net of taxes					$ 0
Adjusted balance, beginning of period					(907)
Other comprehensive income before reclassifications		334	2,026
Increase (decrease) due to amounts reclassified from AOCI		(114)	8
Total other comprehensive income		220	2,034
Balance, end of period		(579)	1,127
Debt valuation adjustment (DVA)
Change in accumulated other comprehensive income (loss)
Balance, beginning of period		(352)	0
Adjustment to opening balance, net of taxes					(15)
Adjusted balance, beginning of period					(15)
Other comprehensive income before reclassifications		(55)	192
Increase (decrease) due to amounts reclassified from AOCI		(5)	1
Total other comprehensive income		(60)	193
Balance, end of period		(412)	178
Cash flow hedges
Change in accumulated other comprehensive income (loss)
Balance, beginning of period		(560)	(617)
Adjustment to opening balance, net of taxes					0
Adjusted balance, beginning of period					(617)
Other comprehensive income before reclassifications		24	291
Increase (decrease) due to amounts reclassified from AOCI		(26)	26
Total other comprehensive income		(2)	317
Balance, end of period		(562)	(300)
Benefit plans
Change in accumulated other comprehensive income (loss)
Balance, beginning of period		(5,164)	(5,116)
Adjustment to opening balance, net of taxes					0
Adjusted balance, beginning of period					(5,116)
Other comprehensive income before reclassifications		(49)	(500)
Increase (decrease) due to amounts reclassified from AOCI		37	35
Total other comprehensive income		(12)	(465)
Balance, end of period		(5,176)	(5,581)
Foreign currency translation adjustment (CTA), net of hedges
Change in accumulated other comprehensive income (loss)
Balance, beginning of period		(25,506)	(22,704)
Adjustment to opening balance, net of taxes					0
Adjusted balance, beginning of period					(22,704)
Other comprehensive income before reclassifications		1,465	654
Increase (decrease) due to amounts reclassified from AOCI		(147)	0
Total other comprehensive income		1,318	654
Balance, end of period		(24,188)	(22,050)
Accumulated other comprehensive income (loss)
Change in accumulated other comprehensive income (loss)
Balance, beginning of period		(32,381)	(29,344)
Adjustment to opening balance, net of taxes	[1]			$ 0	(15)
Adjusted balance, beginning of period				$ (32,381)	$ (29,359)
Other comprehensive income before reclassifications		1,719	2,663
Increase (decrease) due to amounts reclassified from AOCI		(255)	70
Total other comprehensive income		1,464	2,733
Balance, end of period		$ (30,917)	$ (26,626)

[1] See Note 1 to the Consolidated Financial Statements for additional details.