Accumulated Other Comprehensive Income/(Loss) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Unrealized gains/(losses) on AFS securities:
Net change, unrealized gains/(losses) on AFS securities	$ 89	$ 994
Translation adjustments:
Net change after tax	(10)	(2)
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax [Abstract]
Net change	77	59
Defined benefit pension and OPEB plans:
Net change, defined benefit pension and OPEB plans	85	26
Total other comprehensive income, after–tax	241	1,077
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	225	1,621
Net unrealized gains/(losses) arising during the period tax effect	(104)	(609)
Net unrealized gains/(losses) arising during the period after tax	121	1,012
Reclassification adjustment for realized (gains)/losses included in net income before tax	(52)	(30)
Reclassification adjustment for realized (gains)/losses included in net income tax effect	20	12
Reclassification adjustment for realized (gains)/losses included in net income after tax	(32)	(18)
Net change before tax	173	1,591
Net change tax effect	(84)	(597)
Net change, unrealized gains/(losses) on AFS securities	89	994
Translation adjustments, net of hedges
Translation adjustments:
Translation before tax	(1,000)	154
Translation tax effect	378	(63)
Translation after tax	(622)	91
Hedges before tax	993	(154)
Hedges tax effect	(381)	61
Hedges after tax	612	(93)
Net change before tax	(7)	0
Net change tax effect	(3)	(2)
Net change after tax	(10)	(2)
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	(49)	72
Net unrealized gains/(losses) arising during the period tax effect	18	(30)
Net unrealized gains/(losses) arising during the period after tax	(31)	42
Reclassification adjustment for realized (gains)/losses included in net income before tax	175	27
Reclassification adjustment for realized (gains)/losses included in net income tax effect	(67)	(10)
Reclassification adjustment for realized (gains)/losses included in net income after tax	108	17
Net change before tax	126	99
Net change tax effect	(49)	(40)
Net change	77	59
Defined benefit pension and OPEB plans
Defined benefit pension and OPEB plans:
Net gains/(losses) arising during the period before tax	60	69
Net gains/(losses) arising during the period tax effect	(24)	(26)
Net gains/(losses) arising during the period after tax	36	43
Reclassification adjustments included in net income, amortization of net loss before tax	71	18
Reclassification adjustments included in net income, amortization of net loss tax effect	(27)	(8)
Reclassification adjustments included in net income, amortization of net loss after tax	44	10
Reclassification adjustments included in net income, prior service costs/(credits) before tax	(9)	(10)
Reclassification adjustments included in net income, prior service costs/(credits) tax effect	3	4
Reclassification adjustments included in net income, prior service costs/(credits) after tax	(6)	(6)
Foreign exchange and other before tax	33	(4)
Foreign exchange and other tax effect	(22)	(17)
Foreign exchange and other after tax	11	(21)
Net change before tax	155	73
Net change tax effect	(70)	(47)
Net change, defined benefit pension and OPEB plans	85	26
Accumulated other comprehensive income/(loss)
Defined benefit pension and OPEB plans:
Total other comprehensive income/(loss) before tax	447	1,763
Total other comprehensive income/(loss) tax effect	(206)	(686)
Total other comprehensive income, after–tax	$ 241	$ 1,077