Accumulated Other Comprehensive Income/(Loss) (Details) - USD ($) $ in Millions	3 Months Ended			6 Months Ended
	Jun. 30, 2015	Mar. 31, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Unrealized gains/(losses) on AFS securities:
Net change, unrealized gains/(losses) on AFS securities	$ (1,419)		$ 1,075	$ (1,330)	$ 2,069
Translation adjustments:
Net change after tax	3		12	(7)	10
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax [Abstract]
Net change	80		68	157	127
Defined benefit pension and OPEB plans:
Net change, defined benefit pension and OPEB plans	8		7	93	33
Total other comprehensive income, after–tax	(1,328)		1,162	(1,087)	2,239
Net losses reclassified from AOCI to other income		$ 150
Unrealized gains/(losses) on investment securities
Unrealized gains/(losses) on AFS securities:
Net unrealized gains/(losses) arising during the period before tax	(2,343)		1,778	(2,118)	3,399
Net unrealized gains/(losses) arising during the period tax effect	952		(695)	848	(1,304)
Net unrealized gains/(losses) arising during the period after tax	(1,391)		1,083	(1,270)	2,095
Reclassification adjustment for realized (gains)/losses included in net income before tax	(44)		(12)	(96)	(42)
Reclassification adjustment for realized (gains)/losses included in net income tax effect	16		4	36	16
Reclassification adjustment for realized (gains)/losses included in net income after tax	(28)		(8)	(60)	(26)
Net change before tax	(2,387)		1,766	(2,214)	3,357
Net change tax effect	968		(691)	884	(1,288)
Net change, unrealized gains/(losses) on AFS securities	(1,419)		1,075	(1,330)	2,069
Translation adjustments, net of hedges
Translation adjustments:
Translation before tax	267		218	(733)	372
Translation tax effect	(117)		(79)	261	(142)
Translation after tax	150		139	(472)	230
Hedges before tax	(250)		(208)	743	(362)
Hedges tax effect	103		81	(278)	142
Hedges after tax	(147)		(127)	465	(220)
Net change before tax	17		10	10	10
Net change tax effect	(14)		2	(17)	0
Net change after tax	3		12	(7)	10
Cash flow hedges
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax [Abstract]
Net unrealized gains/(losses) arising during the period before tax	120		143	71	215
Net unrealized gains/(losses) arising during the period tax effect	(46)		(57)	(28)	(87)
Net unrealized gains/(losses) arising during the period after tax	74		86	43	128
Reclassification adjustment for realized (gains)/losses included in net income before tax	7		(29)	182	(2)
Reclassification adjustment for realized (gains)/losses included in net income tax effect	(1)		11	(68)	1
Reclassification adjustment for realized (gains)/losses included in net income after tax	6		(18)	114	(1)
Net change before tax	127		114	253	213
Net change tax effect	(47)		(46)	(96)	(86)
Net change	80		68	157	127
Defined benefit pension and OPEB plans
Defined benefit pension and OPEB plans:
Net gains/(losses) arising during the period before tax	41		19	101	88
Net gains/(losses) arising during the period tax effect	(15)		(8)	(39)	(34)
Net gains/(losses) arising during the period after tax	26		11	62	54
Reclassification adjustments included in net income, amortization of net loss before tax	70		19	141	37
Reclassification adjustments included in net income, amortization of net loss tax effect	(26)		(7)	(53)	(15)
Reclassification adjustments included in net income, amortization of net loss after tax	44		12	88	22
Reclassification adjustments included in net income, prior service costs/(credits) before tax	(9)		(12)	(18)	(22)
Reclassification adjustments included in net income, prior service costs/(credits) tax effect	4		5	7	9
Reclassification adjustments included in net income, prior service costs/(credits) after tax	(5)		(7)	(11)	(13)
Foreign exchange and other before tax	(33)		(15)	0	(19)
Foreign exchange and other tax effect	(24)		6	(46)	(11)
Foreign exchange and other after tax	(57)		(9)	(46)	(30)
Net change before tax	(69)		(11)	(224)	(84)
Net change tax effect	(61)		(4)	(131)	(51)
Net change, defined benefit pension and OPEB plans	8		7	93	33
Accumulated other comprehensive income/(loss)
Defined benefit pension and OPEB plans:
Total other comprehensive income/(loss) before tax	(2,174)		1,901	(1,727)	3,664
Total other comprehensive income/(loss) tax effect	846		(739)	640	(1,425)
Total other comprehensive income, after–tax	$ (1,328)		$ 1,162	$ (1,087)	$ 2,239