Shareholders' Equity - Accumulated Other Comprehensive Income by Component (Details) - USD ($) $ in Millions	3 Months Ended						9 Months Ended		12 Months Ended
	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ 24,204	$ 24,750	$ 25,191	$ 25,767	$ 26,224	$ 27,363	$ 25,191	$ 27,363	$ 27,363
Other comprehensive income (loss) before reclassifications							163	(3,232)
Increase (decrease) due to amounts reclassified from accumulated other comprehensive income							503	97
Other comprehensive income (loss)	213	14	439	(581)	(989)	(1,565)	666	(3,135)
Ending balance	23,621	24,204	24,750	25,648	25,767	26,224	23,621	25,648	25,191
AFS transferred to HTM							(578)		(749)
Accumulated Other Comprehensive Income (Loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(3,258)	(3,272)	(3,711)	(3,687)	(2,698)	(1,133)	(3,711)	(1,133)	(1,133)
Other comprehensive income (loss)	213	14	439	(581)	(989)	(1,565)
Ending balance	(3,045)	$ (3,258)	(3,272)	(4,268)	$ (3,687)	(2,698)	(3,045)	(4,268)	(3,711)
Net Unrealized Gains (Losses) on Cash Flow Hedges
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance			(359)			(2)	(359)	(2)	(2)
Other comprehensive income (loss) before reclassifications							83	(344)
Increase (decrease) due to amounts reclassified from accumulated other comprehensive income							113	(6)
Other comprehensive income (loss)							196	(350)
Ending balance	(163)			(352)			(163)	(352)	(359)
Net Unrealized Gains (Losses) on Investment Securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance			(1,817)			(50)	(1,817)	(50)	(50)
Other comprehensive income (loss) before reclassifications							49	(2,041)
Increase (decrease) due to amounts reclassified from accumulated other comprehensive income							378	84
Other comprehensive income (loss)							427	(1,957)
Ending balance	(1,390)			(2,007)			(1,390)	(2,007)	(1,817)
Net Unrealized Losses on Retirement Plans
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance			(143)			(130)	(143)	(130)	(130)
Other comprehensive income (loss) before reclassifications							0	(1)
Increase (decrease) due to amounts reclassified from accumulated other comprehensive income							12	19
Other comprehensive income (loss)							12	18
Ending balance	(131)			(112)			(131)	(112)	(143)
Foreign Currency Translation
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance			(1,751)			(1,019)	(1,751)	(1,019)	(1,019)
Other comprehensive income (loss) before reclassifications							(145)	(1,569)
Increase (decrease) due to amounts reclassified from accumulated other comprehensive income							0	0
Other comprehensive income (loss)							(145)	(1,569)
Ending balance	(1,896)			(2,588)			(1,896)	(2,588)	(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	359	68	68
Other comprehensive income (loss) before reclassifications							176	723
Increase (decrease) due to amounts reclassified from accumulated other comprehensive income							0	0
Other comprehensive income (loss)							176	723
Ending balance	$ 535			$ 791			$ 535	$ 791	$ 359