Investment Securities - Gross Unrealized Losses (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Available-for-sale investment securities with gross unrealized losses and length of time
Estimated Fair Value, Less than 12 months	$ 0	$ 4,311
Estimated Fair Value, 12 months or more	1,154	52
Available-for-sale investment securities with gross unrealized losses
Gross Unrealized Losses, Less than 12 months	0	(83)
Gross Unrealized Losses, 12 months or more	(19)	(1)
State and municipal obligations
Available-for-sale investment securities with gross unrealized losses and length of time
Estimated Fair Value, Less than 12 months	0	52
Estimated Fair Value, 12 months or more	33	0
Available-for-sale investment securities with gross unrealized losses
Gross Unrealized Losses, Less than 12 months	0	(10)
Gross Unrealized Losses, 12 months or more	(6)	0
U.S. Government treasury obligations
Available-for-sale investment securities with gross unrealized losses and length of time
Estimated Fair Value, Less than 12 months	0	3,710
Estimated Fair Value, 12 months or more	1,114	52
Available-for-sale investment securities with gross unrealized losses
Gross Unrealized Losses, Less than 12 months	0	(72)
Gross Unrealized Losses, 12 months or more	(12)	(1)
Mortgage-backed securities
Available-for-sale investment securities with gross unrealized losses and length of time
Estimated Fair Value, Less than 12 months	0	0
Estimated Fair Value, 12 months or more	7	0
Available-for-sale investment securities with gross unrealized losses
Gross Unrealized Losses, Less than 12 months	0	0
Gross Unrealized Losses, 12 months or more	(1)	0
Foreign government bonds and obligations
Available-for-sale investment securities with gross unrealized losses and length of time
Estimated Fair Value, Less than 12 months	0	549
Estimated Fair Value, 12 months or more	0	0
Available-for-sale investment securities with gross unrealized losses
Gross Unrealized Losses, Less than 12 months	0	(1)
Gross Unrealized Losses, 12 months or more	$ 0	$ 0

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Debt Securities, Available-for-sale, Unrealized Loss Position1

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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.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 326
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Amount of accumulated unrealized loss on 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 12 months or longer, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

+ References

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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 less than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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