Securities - Gross Unrealized Losses and Related Fair Values (Detail) $ in Millions	Dec. 31, 2024 USD ($) security	Dec. 31, 2023 USD ($) security
Debt Securities, Available-for-sale [Line Items]
Number of securities available for sale in one year or less \| security	40	22
Securities available-for-sale gross unrealized losses one year or less	$ (45)	$ (2)
Securities available-for-sale aggregate fair value of investment one year or less	$ 6,462	$ 2,889
Number of Securities available for sale greater than one year \| security	319	495
Securities available-for-sale gross unrealized losses greater than one year	$ (2,253)	$ (2,308)
Securities available-for-sale aggregate fair value of investment greater than one year	$ 14,384	$ 20,659
U.S. Treasury
Debt Securities, Available-for-sale [Line Items]
Number of securities available for sale in one year or less \| security	14	3
Securities available-for-sale gross unrealized losses one year or less	$ (15)	$ (1)
Securities available-for-sale aggregate fair value of investment one year or less	$ 3,402	$ 1,008
Number of Securities available for sale greater than one year \| security	38	41
Securities available-for-sale gross unrealized losses greater than one year	$ (190)	$ (224)
Securities available-for-sale aggregate fair value of investment greater than one year	$ 4,055	$ 4,906
U.S. Government sponsored enterprises
Debt Securities, Available-for-sale [Line Items]
Number of securities available for sale in one year or less \| security	0	2
Securities available-for-sale gross unrealized losses one year or less	$ 0	$ 0
Securities available-for-sale aggregate fair value of investment one year or less	$ 0	$ 80
Number of Securities available for sale greater than one year \| security	137	293
Securities available-for-sale gross unrealized losses greater than one year	$ (1,008)	$ (1,183)
Securities available-for-sale aggregate fair value of investment greater than one year	$ 3,871	$ 7,701
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	4	0
Securities available-for-sale gross unrealized losses one year or less	$ (28)	$ 0
Securities available-for-sale aggregate fair value of investment one year or less	$ 526	$ 0
Number of Securities available for sale greater than one year \| security	137	151
Securities available-for-sale gross unrealized losses greater than one year	$ (1,043)	$ (887)
Securities available-for-sale aggregate fair value of investment greater than one year	$ 6,311	$ 7,765
Asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Number of securities available for sale in one year or less \| security	0	0
Securities available-for-sale gross unrealized losses one year or less	$ 0	$ 0
Securities available-for-sale aggregate fair value of investment one year or less	$ 0	$ 0
Number of Securities available for sale greater than one year \| security	6	6
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	$ 97	$ 104
Foreign debt securities
Debt Securities, Available-for-sale [Line Items]
Number of securities available for sale in one year or less \| security	22	17
Securities available-for-sale gross unrealized losses one year or less	$ (2)	$ (1)
Securities available-for-sale aggregate fair value of investment one year or less	$ 2,534	$ 1,801
Number of Securities available for sale greater than one year \| security	1	4
Securities available-for-sale gross unrealized losses greater than one year	$ 0	$ (2)
Securities available-for-sale aggregate fair value of investment greater than one year	$ 50	$ 183

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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