Accumulated Other Comprehensive Loss (Reclassification Out of Accumulated Other Comprehensive Loss) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before tax	$ (2,142)	$ (790)
Other comprehensive income (loss), tax effect	509	186
Other comprehensive income (loss), net of tax	(1,633)	(604)
Investment securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net unrealized gains (losses) arising during the period, before tax	(2,120)	(736)
Net unrealized gains (losses) arising during the period, tax	503	174
Net unrealized gains (losses) arising during the period, net of tax	(1,617)	(562)
Net realized gains reclassified to income from continuing operations, before tax	18	32
Net realized gains reclassified to income from continuing operations, tax	(4)	(7)
Net realized gains reclassified to income from continuing operations, net of tax	14	25
Other comprehensive income (loss), before tax	(2,138)	(768)
Other comprehensive income (loss), tax effect	507	181
Other comprehensive income (loss), net of tax	(1,631)	(587)
Translation adjustments and net investment hedges
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before tax	3	3
Other comprehensive income (loss), tax effect	0	(1)
Other comprehensive income (loss), net of tax	3	2
Net investment hedges
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before tax	(3)	(2)
Other comprehensive income (loss), tax effect	1	1
Other comprehensive income (loss), net of tax	(2)	(1)
Cash flow hedges
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net realized gains reclassified to income from continuing operations, before tax	6	21
Net realized gains reclassified to income from continuing operations, tax	(1)	(4)
Net realized gains reclassified to income from continuing operations, net of tax	5	17
Defined benefit pension plans
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before tax	2	(2)
Other comprehensive income (loss), tax effect	0	1
Other comprehensive income (loss), net of tax	$ 2	$ (1)