Shareholders' Equity - Accumulated Other Comprehensive Income by Component (Details) - USD ($) $ in Millions	3 Months Ended				6 Months Ended		12 Months Ended
	Jun. 30, 2024	Mar. 31, 2024	Jun. 30, 2023	Mar. 31, 2023	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2023
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ 24,433	$ 23,799	$ 24,750	$ 25,191	$ 23,799	$ 25,191	$ 25,191
Other comprehensive income (loss) before reclassifications					(124)	260
Increase (decrease) due to amounts reclassified from accumulated other comprehensive income					164	193
Other comprehensive income (loss)	55	(15)	14	439	40	453
Ending balance	24,762	24,433	24,204	24,750	24,762	24,204	23,799
AFS transferred to HTM					(454)		(530)
Accumulated Other Comprehensive Income (Loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(2,369)	(2,354)	(3,272)	(3,711)	(2,354)	(3,711)	(3,711)
Other comprehensive income (loss)	55	(15)	14	439
Ending balance	(2,314)	(2,369)	(3,258)	(3,272)	(2,314)	(3,258)	(2,354)
Net Unrealized Gains (Losses) on Cash Flow Hedges
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance		(131)		(359)	(131)	(359)	(359)
Other comprehensive income (loss) before reclassifications					30	58
Increase (decrease) due to amounts reclassified from accumulated other comprehensive income					(107)	75
Other comprehensive income (loss)					(77)	133
Ending balance	(208)		(226)		(208)	(226)	(131)
Net Unrealized Gains (Losses) on Investment Securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance		(947)		(1,817)	(947)	(1,817)	(1,817)
Other comprehensive income (loss) before reclassifications					(45)	44
Increase (decrease) due to amounts reclassified from accumulated other comprehensive income					270	106
Other comprehensive income (loss)					225	150
Ending balance	(722)		(1,667)		(722)	(1,667)	(947)
Net Unrealized Losses on Retirement Plans
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance		(145)		(143)	(145)	(143)	(143)
Other comprehensive income (loss) before reclassifications					6	0
Increase (decrease) due to amounts reclassified from accumulated other comprehensive income					1	12
Other comprehensive income (loss)					7	12
Ending balance	(138)		(131)		(138)	(131)	(145)
Foreign Currency Translation
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance		(1,400)		(1,751)	(1,400)	(1,751)	(1,751)
Other comprehensive income (loss) before reclassifications					(358)	207
Increase (decrease) due to amounts reclassified from accumulated other comprehensive income					0	0
Other comprehensive income (loss)					(358)	207
Ending balance	(1,758)		(1,544)		(1,758)	(1,544)	(1,400)
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		$ 269		$ 359	269	359	359
Other comprehensive income (loss) before reclassifications					243	(49)
Increase (decrease) due to amounts reclassified from accumulated other comprehensive income					0	0
Other comprehensive income (loss)					243	(49)
Ending balance	$ 512		$ 310		$ 512	$ 310	$ 269