Accumulated Other Comprehensive Income/(Loss) - Components of Other Comprehensive Income/(Loss) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Unrealized gains/(losses) on AFS securities:
Net change, unrealized gains/(losses) on AFS securities	$ (4,070)	$ 3,303	$ 1,067
Translation adjustments:
Net change after tax	(41)	(69)	(279)
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax [Abstract]
Net change	(259)	69	(155)
Defined benefit pension and OPEB plans:
Net change, defined benefit pension and OPEB plans	1,467	(145)	(690)
Total other comprehensive income/(loss), after-tax	(2,903)	3,158	(57)
Unrealized gains/(losses) on AFS securities [Member]
Unrealized gains/(losses) on AFS securities:
Net unrealized gains/(losses) arising during the period before tax	(5,987)	7,521	3,361
Net unrealized gains/(losses) arising during the period tax effect	2,323	(2,930)	(1,322)
Net unrealized gains/(losses) arising during the period after tax	(3,664)	4,591	2,039
Reclassification adjustment for realized (gains)/losses included in net income before tax	(667)	(2,110)	(1,593)
Reclassification adjustment for realized (gains)/losses included in net income tax effect	261	822	621
Reclassification adjustment for realized (gains)/losses included in net income after tax	(406)	(1,288)	(972)
Net change before tax	(6,654)	5,411	1,768
Net change tax effect	2,584	(2,108)	(701)
Net change, unrealized gains/(losses) on AFS securities	(4,070)	3,303	1,067
Translation adjustments, net of hedges [Member]
Translation adjustments:
Translation before tax	(807)	(26)	(672)
Translation tax effect	295	8	255
Translation after tax	(512)	(18)	(417)
Hedges before tax	773	(82)	226
Hedges tax effect	(302)	31	(88)
Hedges after tax	471	(51)	138
Net change before tax	(34)	(108)	(446)
Net change tax effect	(7)	39	167
Net change after tax	(41)	(69)	(279)
Cash flow hedges [Member]
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax [Abstract]
Net unrealized gains/(losses) arising during the period before tax	(525)	141	50
Net unrealized gains/(losses) arising during the period tax effect	206	(55)	(19)
Net unrealized gains/(losses) arising during the period after tax	(319)	86	31
Reclassification adjustment for realized (gains)/losses included in net income before tax	101	(28)	(301)
Reclassification adjustment for realized (gains)/losses included in net income tax effect	(41)	11	115
Reclassification adjustment for realized (gains)/losses included in net income after tax	60	(17)	(186)
Net change before tax	(424)	113	(251)
Net change tax effect	165	(44)	96
Net change	(259)	69	(155)
Defined benefit pension and OPEB plans [Member]
Defined benefit pension and OPEB plans:
Prior service credits arising during the period before tax	0	6	0
Prior service credits arising during the period tax effect	0	(2)	0
Prior service credits arising during the period after tax	0	4	0
Net gains/(losses) arising during the period before tax	2,055	(537)	(1,290)
Net gains/(losses) arising during the period tax effect	(750)	228	502
Net gains/(losses) arising during the period after tax	1,305	(309)	(788)
Reclassification adjustments included in net income, amortization of net loss before tax	321	324	214
Reclassification adjustments included in net income, amortization of net loss tax effect	(124)	(126)	(83)
Reclassification adjustments included in net income, amortization of net loss after tax	197	198	131
Reclassification adjustments included in net income, prior service costs/(credits) before tax	(43)	(41)	(52)
Reclassification adjustments included in net income, prior service costs/(credits) tax effect	17	16	20
Reclassification adjustments included in net income, prior service costs/(credits) after tax	(26)	(25)	(32)
Foreign exchange and other before tax	(14)	(21)	(1)
Foreign exchange and other tax effect	5	8	0
Foreign exchange and other after tax	(9)	(13)	(1)
Net change before tax	2,319	(269)	(1,129)
Net change tax effect	(852)	124	439
Net change, defined benefit pension and OPEB plans	1,467	(145)	(690)
Accumulated other comprehensive income/(loss) [Member]
Defined benefit pension and OPEB plans:
Total other comprehensive income/(loss) before tax	(4,793)	5,147	(58)
Total other comprehensive income/(loss) tax effect	1,890	(1,989)	1
Total other comprehensive income/(loss), after-tax	$ (2,903)	$ 3,158	$ (57)