Securities - Gross Unrealized Losses and Related Fair Values (Detail) $ in Millions	Mar. 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	9	22
Securities available-for-sale gross unrealized losses one year or less	$ (2)	$ (2)
Securities available-for-sale aggregate fair value of investment one year or less	$ 1,339	$ 2,889
Number of Securities available for sale greater than one year \| security	481	495
Securities available-for-sale gross unrealized losses greater than one year	$ (2,459)	$ (2,308)
Securities available-for-sale aggregate fair value of investment greater than one year	$ 19,588	$ 20,659
U.S. Treasury
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	$ 1,008
Number of Securities available for sale greater than one year \| security	40	41
Securities available-for-sale gross unrealized losses greater than one year	$ (175)	$ (224)
Securities available-for-sale aggregate fair value of investment greater than one year	$ 4,636	$ 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	290	293
Securities available-for-sale gross unrealized losses greater than one year	$ (1,269)	$ (1,183)
Securities available-for-sale aggregate fair value of investment greater than one year	$ 7,336	$ 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	2	0
Securities available-for-sale gross unrealized losses one year or less	$ (2)	$ 0
Securities available-for-sale aggregate fair value of investment one year or less	$ 118	$ 0
Number of Securities available for sale greater than one year \| security	142	151
Securities available-for-sale gross unrealized losses greater than one year	$ (1,001)	$ (887)
Securities available-for-sale aggregate fair value of investment greater than one year	$ 7,353	$ 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	$ (13)	$ (12)
Securities available-for-sale aggregate fair value of investment greater than one year	$ 102	$ 104
Foreign debt securities
Debt Securities, Available-for-sale [Line Items]
Number of securities available for sale in one year or less \| security	7	17
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	$ 1,221	$ 1,801
Number of Securities available for sale greater than one year \| security	3	4
Securities available-for-sale gross unrealized losses greater than one year	$ (1)	$ (2)
Securities available-for-sale aggregate fair value of investment greater than one year	$ 161	$ 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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