Shareholders' Equity - Accumulated Other Comprehensive Income by Component (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2023	Mar. 31, 2022	Dec. 31, 2022
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ 25,191	$ 27,363	$ 27,363
Other comprehensive income (loss) before reclassifications	338	(1,564)
Increase (decrease) due to amounts reclassified from accumulated other comprehensive income	101	(1)
Other comprehensive income (loss)	439	(1,565)
Ending balance	24,750	26,224	25,191
AFS transferred to HTM	(697)		(749)
Accumulated Other Comprehensive Income (Loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(3,711)	(1,133)	(1,133)
Other comprehensive income (loss)	439	(1,565)
Ending balance	(3,272)	(2,698)	(3,711)
Net Unrealized Gains (Losses) on Cash Flow Hedges
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(359)	(2)	(2)
Other comprehensive income (loss) before reclassifications	14	(178)
Increase (decrease) due to amounts reclassified from accumulated other comprehensive income	37	(16)
Other comprehensive income (loss)	51	(194)
Ending balance	(308)	(196)	(359)
Net Unrealized Gains (Losses) on Investment Securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(1,817)	(50)	(50)
Other comprehensive income (loss) before reclassifications	194	(1,288)
Increase (decrease) due to amounts reclassified from accumulated other comprehensive income	52	0
Other comprehensive income (loss)	246	(1,288)
Ending balance	(1,571)	(1,338)	(1,817)
Net Unrealized Losses on Retirement Plans
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(143)	(130)	(130)
Other comprehensive income (loss) before reclassifications	0	0
Increase (decrease) due to amounts reclassified from accumulated other comprehensive income	12	15
Other comprehensive income (loss)	12	15
Ending balance	(131)	(115)	(143)
Foreign Currency Translation
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(1,751)	(1,019)	(1,019)
Other comprehensive income (loss) before reclassifications	172	(162)
Increase (decrease) due to amounts reclassified from accumulated other comprehensive income	0	0
Other comprehensive income (loss)	172	(162)
Ending balance	(1,579)	(1,181)	(1,751)
Net Unrealized Gains (Losses) on Hedges of Net Investments in Non-U.S. Subsidiaries
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	359	68	68
Other comprehensive income (loss) before reclassifications	(42)	64
Increase (decrease) due to amounts reclassified from accumulated other comprehensive income	0	0
Other comprehensive income (loss)	(42)	64
Ending balance	$ 317	$ 132	$ 359