Accumulated Other Comprehensive Income/(Loss) (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Unrealized gains/(losses) on investment securities:
Total other comprehensive income/(loss), after–tax	$ 1,529	$ 1,371	$ (5,416)	$ 7,220
Accumulated other comprehensive income/(loss)
Unrealized gains/(losses) on investment securities:
Net change, Pre-tax	1,917	1,628	(6,884)	9,759
Net change, Tax effect	(388)	(257)	1,468	(2,539)
Total other comprehensive income/(loss), after–tax	1,529	1,371	(5,416)	7,220
Unrealized gains/(losses) on investment securities
Unrealized gains/(losses) on investment securities:
Net unrealized gains/(losses) arising during the period/Translation, Pre-tax	727	3,642	(4,966)	5,351
Net unrealized gains/(losses) arising during the period/Translation, Tax effect	(171)	(878)	1,194	(1,291)
Net unrealized gains/(losses) arising during the period/Translation, After-tax	556	2,764	(3,772)	4,060
Reclassification, Pre-tax	155	(26)	141	(259)
Reclassification, Tax effect	(37)	6	(34)	62
Reclassifications, After-tax	118	(20)	107	(197)
Net change, Pre-tax	882	3,616	(4,825)	5,092
Net change, Tax effect	(208)	(872)	1,160	(1,229)
Total other comprehensive income/(loss), after–tax	674	2,744	(3,665)	3,863
Translation adjustments
Unrealized gains/(losses) on investment securities:
Net unrealized gains/(losses) arising during the period/Translation, Pre-tax	280	405	(920)	(1,187)
Net unrealized gains/(losses) arising during the period/Translation, Tax effect	(10)	46	29	101
Net unrealized gains/(losses) arising during the period/Translation, After-tax	270	451	(891)	(1,086)
Reclassification, Pre-tax	(270)	(405)	930	1,184
Reclassification, Tax effect	64	96	(225)	(286)
Reclassifications, After-tax	(206)	(309)	705	898
Net change, Pre-tax	10	0	10	(3)
Net change, Tax effect	54	142	(196)	(185)
Total other comprehensive income/(loss), after–tax	64	142	(186)	(188)
Fair value hedges, net change
Unrealized gains/(losses) on investment securities:
Net change, Pre-tax	(31)	21	(68)	136
Net change, Tax effect	8	(5)	17	(32)
Total other comprehensive income/(loss), after–tax	(23)	16	(51)	104
Cash flow hedges
Unrealized gains/(losses) on investment securities:
Net unrealized gains/(losses) arising during the period/Translation, Pre-tax	1,118	402	(1,577)	3,653
Net unrealized gains/(losses) arising during the period/Translation, Tax effect	(269)	(97)	378	(877)
Net unrealized gains/(losses) arising during the period/Translation, After-tax	849	305	(1,199)	2,776
Reclassification, Pre-tax	(340)	(93)	(604)	(101)
Reclassification, Tax effect	82	22	145	24
Reclassifications, After-tax	(258)	(71)	(459)	(77)
Net change, Pre-tax	778	309	(2,181)	3,552
Net change, Tax effect	(187)	(75)	523	(853)
Total other comprehensive income/(loss), after–tax	591	234	(1,658)	2,699
Defined benefit pension and OPEB plans, net change
Unrealized gains/(losses) on investment securities:
Net change, Pre-tax	2	(4)	93	41
Net change, Tax effect	7	(3)	(16)	(15)
Total other comprehensive income/(loss), after–tax	9	(7)	77	26
DVA on fair value option elected liabilities, net change
Unrealized gains/(losses) on investment securities:
Net change, Pre-tax	276	(2,314)	87	941
Net change, Tax effect	(62)	556	(20)	(225)
Total other comprehensive income/(loss), after–tax	$ 214	$ (1,758)	$ 67	$ 716

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