Securities - Gross Unrealized Losses and Related Fair Values (Detail) $ in Millions	Dec. 31, 2023 USD ($) security	Dec. 31, 2022 USD ($) security
Debt Securities, Available-for-sale [Line Items]
Number of securities available for sale in one year or less \| security	22	369
Securities available-for-sale gross unrealized losses one year or less	$ (2)	$ (957)
Securities available-for-sale aggregate fair value of investment one year or less	$ 2,889	$ 10,968
Number of Securities available for sale greater than one year \| security	495	159
Securities available-for-sale gross unrealized losses greater than one year	$ (2,308)	$ (2,068)
Securities available-for-sale aggregate fair value of investment greater than one year	$ 20,659	$ 12,206
U.S. Treasury
Debt Securities, Available-for-sale [Line Items]
Number of securities available for sale in one year or less \| security	3	22
Securities available-for-sale gross unrealized losses one year or less	$ (1)	$ (105)
Securities available-for-sale aggregate fair value of investment one year or less	$ 1,008	$ 2,800
Number of Securities available for sale greater than one year \| security	41	19
Securities available-for-sale gross unrealized losses greater than one year	$ (224)	$ (137)
Securities available-for-sale aggregate fair value of investment greater than one year	$ 4,906	$ 2,013
U.S. Government sponsored enterprises
Debt Securities, Available-for-sale [Line Items]
Number of securities available for sale in one year or less \| security	2	233
Securities available-for-sale gross unrealized losses one year or less	$ 0	$ (316)
Securities available-for-sale aggregate fair value of investment one year or less	$ 80	$ 3,270
Number of Securities available for sale greater than one year \| security	293	79
Securities available-for-sale gross unrealized losses greater than one year	$ (1,183)	$ (1,102)
Securities available-for-sale aggregate fair value of investment greater than one year	$ 7,701	$ 4,959
U.S. Government agency issued or guaranteed
Debt Securities, Available-for-sale [Line Items]
Number of securities available for sale in one year or less \| security	0	107
Securities available-for-sale gross unrealized losses one year or less	$ 0	$ (534)
Securities available-for-sale aggregate fair value of investment one year or less	$ 0	$ 4,547
Number of Securities available for sale greater than one year \| security	151	55
Securities available-for-sale gross unrealized losses greater than one year	$ (887)	$ (809)
Securities available-for-sale aggregate fair value of investment greater than one year	$ 7,765	$ 4,856
Asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Number of securities available for sale in one year or less \| security	0	3
Securities available-for-sale gross unrealized losses one year or less	$ 0	$ (1)
Securities available-for-sale aggregate fair value of investment one year or less	$ 0	$ 14
Number of Securities available for sale greater than one year \| security	6	3
Securities available-for-sale gross unrealized losses greater than one year	$ (12)	$ (12)
Securities available-for-sale aggregate fair value of investment greater than one year	$ 104	$ 92
Foreign debt securities
Debt Securities, Available-for-sale [Line Items]
Number of securities available for sale in one year or less \| security	17	4
Securities available-for-sale gross unrealized losses one year or less	$ (1)	$ (1)
Securities available-for-sale aggregate fair value of investment one year or less	$ 1,801	$ 337
Number of Securities available for sale greater than one year \| security	4	3
Securities available-for-sale gross unrealized losses greater than one year	$ (2)	$ (8)
Securities available-for-sale aggregate fair value of investment greater than one year	$ 183	$ 286

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for more than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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