Accumulated Other Comprehensive Income/(Loss) (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Unrealized gains/(losses) on investment securities:
Net change, Pre-tax	$ 2,069	$ (39)	$ 3,348	$ (1,426)
Net change, Tax effect	(397)	(36)	(727)	319
Total other comprehensive income/(loss), after–tax	1,672	(75)	2,621	(1,107)
Accumulated other comprehensive income/(loss)
Unrealized gains/(losses) on investment securities:
Total other comprehensive income/(loss), after–tax	1,672	(75)	2,621	(1,107)
Accumulated other comprehensive income/(loss) \| Other income
Unrealized gains/(losses) on investment securities:
Net pre-tax gain (loss) reclassified related to liquidation of legal entity	6		6
Accumulated other comprehensive income/(loss) \| Other expense
Unrealized gains/(losses) on investment securities:
Net pre-tax gain (loss) reclassified related to liquidation of legal entity	1	(174)	1	(174)
Unrealized gains/(losses) on investment securities
Unrealized gains/(losses) on investment securities:
Net unrealized gains/(losses) arising during the period/Translation, Pre-tax	1,491	(376)	3,366	(2,234)
Net unrealized gains/(losses) arising during the period/Translation, Tax effect	(365)	88	(816)	525
Net unrealized gains/(losses) arising during the period/Translation, After-tax	1,126	(288)	2,550	(1,709)
Reclassification, Pre-tax	(44)	80	(57)	325
Reclassification, Tax effect	11	(19)	14	(77)
Reclassifications, After-tax	(33)	61	(43)	248
Net change, Pre-tax	1,447	(296)	3,309	(1,909)
Net change, Tax effect	(354)	69	(802)	448
Total other comprehensive income/(loss), after–tax	1,093	(227)	2,507	(1,461)
Unrealized gains/(losses) on investment securities \| Other income
Unrealized gains/(losses) on investment securities:
Net pre-tax gain (loss) reclassified related to liquidation of legal entity	5		5
Unrealized gains/(losses) on investment securities \| Other expense
Unrealized gains/(losses) on investment securities:
Net pre-tax gain (loss) reclassified related to liquidation of legal entity	5	(23)	5	(23)
Translation adjustments
Unrealized gains/(losses) on investment securities:
Net unrealized gains/(losses) arising during the period/Translation, Pre-tax	123	(1,056)	164	(667)
Net unrealized gains/(losses) arising during the period/Translation, Tax effect	72	208	36	143
Net unrealized gains/(losses) arising during the period/Translation, After-tax	195	(848)	200	(524)
Reclassification, Pre-tax	(128)	1,227	(166)	838
Reclassification, Tax effect	32	(291)	41	(199)
Reclassifications, After-tax	(96)	936	(125)	639
Net change, Pre-tax	(5)	171	(2)	171
Net change, Tax effect	104	(83)	77	(56)
Total other comprehensive income/(loss), after–tax	99	88	75	115
Translation adjustments \| Other income
Unrealized gains/(losses) on investment securities:
Net pre-tax gain (loss) reclassified related to liquidation of legal entity	2		2
Translation adjustments \| Other expense
Unrealized gains/(losses) on investment securities:
Net pre-tax gain (loss) reclassified related to liquidation of legal entity	2	(151)	2	(151)
Fair value hedges, net change
Unrealized gains/(losses) on investment securities:
Net change, Pre-tax	112	(89)	115	(141)
Net change, Tax effect	(26)	21	(27)	33
Total other comprehensive income/(loss), after–tax	86	(68)	88	(108)
Cash flow hedges
Unrealized gains/(losses) on investment securities:
Net unrealized gains/(losses) arising during the period/Translation, Pre-tax	101	(199)	242	(243)
Net unrealized gains/(losses) arising during the period/Translation, Tax effect	(24)	47	(57)	58
Net unrealized gains/(losses) arising during the period/Translation, After-tax	77	(152)	185	(185)
Reclassification, Pre-tax	26	(19)	65	(71)
Reclassification, Tax effect	(6)	5	(15)	17
Reclassifications, After-tax	20	(14)	50	(54)
Net change, Pre-tax	127	(218)	307	(314)
Net change, Tax effect	(30)	52	(72)	75
Total other comprehensive income/(loss), after–tax	97	(166)	235	(239)
Defined benefit pension and OPEB plans
Unrealized gains/(losses) on investment securities:
Net change, Pre-tax	50	53	88	77
Net change, Tax effect	(9)	(15)	(11)	(18)
Total other comprehensive income/(loss), after–tax	41	38	77	59
Net gain/(loss)/Amortization of net loss
Unrealized gains/(losses) on investment securities:
Net unrealized gains/(losses) arising during the period/Translation, Pre-tax	(1)	2	2	25
Net unrealized gains/(losses) arising during the period/Translation, Tax effect	0	0	(2)	(6)
Net unrealized gains/(losses) arising during the period/Translation, After-tax	(1)	2	0	19
Reclassification, Pre-tax	41	26	83	52
Reclassification, Tax effect	(7)	(6)	(16)	(12)
Reclassifications, After-tax	34	20	67	40
Amortization of prior service cost/(credit)
Unrealized gains/(losses) on investment securities:
Reclassification, Pre-tax	1	(6)	2	(12)
Reclassification, Tax effect	(1)	2	(1)	3
Reclassifications, After-tax	0	(4)	1	(9)
Foreign exchange and other
Unrealized gains/(losses) on investment securities:
Reclassification, Pre-tax	9	31	1	12
Reclassification, Tax effect	(1)	(11)	8	(3)
Reclassifications, After-tax	8	20	9	9
DVA on fair value option elected liabilities, net change
Unrealized gains/(losses) on investment securities:
Net change, Pre-tax	338	340	(469)	690
Net change, Tax effect	(82)	(80)	108	(163)
Total other comprehensive income/(loss), after–tax	$ 256	$ 260	$ (361)	$ 527

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