CHANGES IN ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) - Change in Each Compenant of AOCI (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		12 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014	Dec. 31, 2013
Change in accumulated other comprehensive income (loss)
Beginning-of-period balance, net of tax				$ (19,133)
End-of-period balance, net of tax	(24,691)	(19,146)	(23,216)	(19,133)
Net unrealized gains (losses) on investment securities
Change in accumulated other comprehensive income (loss)
Beginning-of-period balance, net of tax	57	(1,640)	(1,640)
Other comprehensive income before reclassifications	742	378
Increase (decrease) due to amounts reclassified from AOCI	(151)	50
Change, net of taxes	591	428
End-of-period balance, net of tax	648	(1,212)
Cash flow hedges
Change in accumulated other comprehensive income (loss)
Beginning-of-period balance, net of tax	(909)	(1,245)	(1,245)
Other comprehensive income before reclassifications	32	46
Increase (decrease) due to amounts reclassified from AOCI	54	72
Change, net of taxes	86	118
End-of-period balance, net of tax	(823)	(1,127)
Benefit plans
Change in accumulated other comprehensive income (loss)
Beginning-of-period balance, net of tax	(5,159)	(3,989)	(3,989)
Other comprehensive income before reclassifications	(131)	(62)
Increase (decrease) due to amounts reclassified from AOCI	41	29
Change, net of taxes	(90)	(33)
End-of-period balance, net of tax	(5,249)	(4,022)
Foreign currency translation adjustment
Change in accumulated other comprehensive income (loss)
Beginning-of-period balance, net of tax	(17,205)	(12,259)	(12,259)
Other comprehensive income before reclassifications	(2,062)	(526)
Increase (decrease) due to amounts reclassified from AOCI	0	0
Change, net of taxes	(2,062)	(526)
End-of-period balance, net of tax	(19,267)	(12,785)	(17,205)
Reclassification for allocation between net unrealized gains (losses) on investment securities to CTA, before tax			137
Reclassification for allocation between net unrealized gains (losses) on investment securities to CTA, net of tax			84
Accumulated other comprehensive income (loss)
Change in accumulated other comprehensive income (loss)
Beginning-of-period balance, net of tax	(23,216)	(19,133)	(19,133)
Other comprehensive income before reclassifications	(1,419)	(164)
Increase (decrease) due to amounts reclassified from AOCI	(56)	151
Change, net of taxes	(1,475)	(13)
End-of-period balance, net of tax	$ (24,691)	$ (19,146)