Shareholders' Equity - Accumulated Other Comprehensive Income by Component (Details) - USD ($) $ in Millions	3 Months Ended						9 Months Ended		12 Months Ended
	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ 24,762	$ 24,433	$ 23,799	$ 24,204	$ 24,750	$ 25,191	$ 23,799	$ 25,191	$ 25,191
Other comprehensive income (loss) before reclassifications							426	163
Increase (decrease) due to amounts reclassified from accumulated other comprehensive income							303	503
Other comprehensive income	689	55	(15)	213	14	439	729	666
Ending balance	25,828	24,762	24,433	23,621	24,204	24,750	25,828	23,621	23,799
AFS transferred to HTM							(415)		(530)
Accumulated Other Comprehensive Income (Loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(2,314)	(2,369)	(2,354)	(3,258)	(3,272)	(3,711)	(2,354)	(3,711)	(3,711)
Other comprehensive income	689	55	(15)	213	14	439
Ending balance	(1,625)	$ (2,314)	(2,369)	(3,045)	$ (3,258)	(3,272)	(1,625)	(3,045)	(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							39	83
Increase (decrease) due to amounts reclassified from accumulated other comprehensive income							(69)	113
Other comprehensive income							(30)	196
Ending balance	(161)			(163)			(161)	(163)	(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							206	49
Increase (decrease) due to amounts reclassified from accumulated other comprehensive income							371	378
Other comprehensive income							577	427
Ending balance	(370)			(1,390)			(370)	(1,390)	(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							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							197	(145)
Increase (decrease) due to amounts reclassified from accumulated other comprehensive income							0	0
Other comprehensive income							197	(145)
Ending balance	(1,203)			(1,896)			(1,203)	(1,896)	(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							(22)	176
Increase (decrease) due to amounts reclassified from accumulated other comprehensive income							0	0
Other comprehensive income							(22)	176
Ending balance	$ 247			$ 535			$ 247	$ 535	$ 269