Accumulated Other Comprehensive Income/(Loss) (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Unrealized gains/(losses) on AFS securities:
Net change, Pre-tax	$ (39)	$ 851	$ (1,426)	$ 1,269
Net change, Tax effect	(36)	(320)	319	(486)
Total other comprehensive income/(loss), after–tax	(75)	531	(1,107)	783
Accumulated other comprehensive income/(loss)
Unrealized gains/(losses) on AFS securities:
Total other comprehensive income/(loss), after–tax			(1,107)	783
Net pre-tax loss reclassified to other expense related to liquidation of legal entity	174	0	174	25
Unrealized gains/(losses) on investment securities
Unrealized gains/(losses) on AFS securities:
Net unrealized gains/(losses) arising during the period/Translation, Pre-tax	(376)	695	(2,234)	1,062
Net unrealized gains/(losses) arising during the period/Translation, Tax effect	88	(259)	525	(390)
Net unrealized gains/(losses) arising during the period/Translation, After-tax	(288)	436	(1,709)	672
Reclassification, Pre-tax	80	34	325	37
Reclassification, Tax effect	(19)	(13)	(77)	(14)
Reclassifications, After-tax	61	21	248	23
Net change, Pre-tax	(296)	729	(1,909)	1,099
Net change, Tax effect	69	(272)	448	(404)
Total other comprehensive income/(loss), after–tax	(227)	457	(1,461)	695
Net pre-tax loss reclassified to other expense related to liquidation of legal entity	23		23	47
Translation adjustments
Unrealized gains/(losses) on AFS securities:
Net unrealized gains/(losses) arising during the period/Translation, Pre-tax	(1,056)	317	(667)	899
Net unrealized gains/(losses) arising during the period/Translation, Tax effect	208	(117)	143	(342)
Net unrealized gains/(losses) arising during the period/Translation, After-tax	(848)	200	(524)	557
Reclassification, Pre-tax	1,227	(319)	838	(875)
Reclassification, Tax effect	(291)	119	(199)	325
Reclassifications, After-tax	936	(200)	639	(550)
Net change, Pre-tax	171	(2)	171	24
Net change, Tax effect	(83)	2	(56)	(17)
Total other comprehensive income/(loss), after–tax	88	0	115	7
Net pre-tax loss reclassified to other expense related to liquidation of legal entity	151		151	72
Fair value hedges
Unrealized gains/(losses) on AFS securities:
Net change, Pre-tax	(89)		(141)
Net change, Tax effect	21		33
Total other comprehensive income/(loss), after–tax	(68)		(108)
Cash flow hedges
Unrealized gains/(losses) on AFS securities:
Net unrealized gains/(losses) arising during the period/Translation, Pre-tax	(199)	23	(243)	82
Net unrealized gains/(losses) arising during the period/Translation, Tax effect	47	(10)	58	(31)
Net unrealized gains/(losses) arising during the period/Translation, After-tax	(152)	13	(185)	51
Reclassification, Pre-tax	(19)	65	(71)	150
Reclassification, Tax effect	5	(25)	17	(57)
Reclassifications, After-tax	(14)	40	(54)	93
Net change, Pre-tax	(218)	88	(314)	232
Net change, Tax effect	52	(35)	75	(88)
Total other comprehensive income/(loss), after–tax	(166)	53	(239)	144
Defined benefit pension and OPEB plans
Unrealized gains/(losses) on AFS securities:
Net change, Pre-tax	53	34	77	19
Net change, Tax effect	(15)	(15)	(18)	(15)
Total other comprehensive income/(loss), after–tax	38	19	59	4
Net gain/(losses)/Amortization of net loss
Unrealized gains/(losses) on AFS securities:
Net unrealized gains/(losses) arising during the period/Translation, Pre-tax	2	6	25	(52)
Net unrealized gains/(losses) arising during the period/Translation, Tax effect	0	(2)	(6)	19
Net unrealized gains/(losses) arising during the period/Translation, After-tax	2	4	19	(33)
Reclassification, Pre-tax	26	62	52	124
Reclassification, Tax effect	(6)	(23)	(12)	(46)
Reclassifications, After-tax	20	39	40	78
Prior service costs/(credits)
Unrealized gains/(losses) on AFS securities:
Reclassification, Pre-tax	(6)	(9)	(12)	(18)
Reclassification, Tax effect	2	4	3	7
Reclassifications, After-tax	(4)	(5)	(9)	(11)
Settlement (gain)/loss
Unrealized gains/(losses) on AFS securities:
Reclassification, Pre-tax			0	(3)
Reclassification, Tax effect			0	1
Reclassifications, After-tax			0	(2)
Foreign exchange and other
Unrealized gains/(losses) on AFS securities:
Reclassification, Pre-tax	31	(25)	12	(32)
Reclassification, Tax effect	(11)	6	(3)	4
Reclassifications, After-tax	20	(19)	9	(28)
DVA on fair value option elected liabilities, net change
Unrealized gains/(losses) on AFS securities:
Net change, Pre-tax	340	2	690	(105)
Net change, Tax effect	(80)	0	(163)	38
Total other comprehensive income/(loss), after–tax	$ 260	$ 2	$ 527	$ (67)

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