Investment Securities - Held-to-Maturity Securities (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Schedule of Held-to-Maturity Securities [Line Items]
Amortized Cost	$ 80,025	$ 84,045
Unrealized Gains	56	12
Unrealized Losses	(8,666)	(9,969)
Fair Value	71,415	74,088
U.S. Treasury and agencies
Schedule of Held-to-Maturity Securities [Line Items]
Amortized Cost	1,296	1,345
Unrealized Gains	0	0
Unrealized Losses	(16)	(35)
Fair Value	1,280	1,310
Residential mortgage-backed securities | Agency
Schedule of Held-to-Maturity Securities [Line Items]
Amortized Cost	76,788	80,997
Unrealized Gains	22	6
Unrealized Losses	(8,648)	(9,929)
Fair Value	68,162	71,074
Commercial mortgage-backed securities | Agency
Schedule of Held-to-Maturity Securities [Line Items]
Amortized Cost	1,699	1,695
Unrealized Gains	31	6
Unrealized Losses	(2)	(5)
Fair Value	1,728	1,696
Other
Schedule of Held-to-Maturity Securities [Line Items]
Amortized Cost	242	8
Unrealized Gains	3	0
Unrealized Losses	0	0
Fair Value	$ 245	$ 8