Accumulated Other Comprehensive Income (Reclassification Out of Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before tax	$ (216)	$ (157)	$ (759)	$ 750
Other comprehensive income (loss), tax effect	51	37	179	(178)
Other comprehensive income (loss), net of tax	(165)	(120)	(580)	572
Investment securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net unrealized gains (losses) arising during the period, before tax	(161)	(92)	(621)	785
Net unrealized gains (losses) arising during the period, tax	38	22	147	(184)
Net unrealized gains (losses) arising during the period, net of tax	(123)	(70)	(474)	601
Net realized gains reclassified to income from continuing operations, before tax	44	43	82	167
Net realized gains reclassified to income from continuing operations, tax	(10)	(10)	(18)	(38)
Net realized gains reclassified to income from continuing operations, net of tax	34	33	64	129
Other comprehensive income (loss), before tax	(205)	(135)	(703)	618
Other comprehensive income (loss), tax effect	48	32	165	(146)
Other comprehensive income (loss), net of tax	(157)	(103)	(538)	472
Translation adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before tax	(4)	3	1	(4)
Other comprehensive income (loss), tax effect	1	(1)	0	1
Other comprehensive income (loss), net of tax	(3)	2	1	(3)
Net investment hedges
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before tax	4	(4)	(1)	3
Other comprehensive income (loss), tax effect	(1)	1	1	(1)
Other comprehensive income (loss), net of tax	3	(3)	0	2
Cash flow hedges
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net unrealized gains (losses) arising during the period, before tax				169
Net unrealized gains (losses) arising during the period, tax				(41)
Net unrealized gains (losses) arising during the period, net of tax				128
Net realized gains reclassified to income from continuing operations, before tax	12	21	55	40
Net realized gains reclassified to income from continuing operations, tax	(3)	(5)	(12)	(10)
Net realized gains reclassified to income from continuing operations, net of tax	9	$ 16	43	30
Other comprehensive income (loss), before tax				129
Other comprehensive income (loss), tax effect				(31)
Other comprehensive income (loss), net of tax				98
Defined benefit pension plans
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net unrealized gains (losses) arising during the period, before tax			(2)
Net unrealized gains (losses) arising during the period, tax			1
Net unrealized gains (losses) arising during the period, net of tax			(1)
Net realized gains reclassified to income from continuing operations, before tax	(1)		(1)
Net realized gains reclassified to income from continuing operations, tax	0		0
Net realized gains reclassified to income from continuing operations, net of tax	$ (1)		(1)
Other comprehensive income (loss), before tax			(1)	4
Other comprehensive income (loss), tax effect			1	(1)
Other comprehensive income (loss), net of tax			$ 0	$ 3