Derivative Financial Instruments - Carrying Value of Hedged Items in Fair Value Hedge (Details) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Derivatives, Fair Value [Line Items]
Carrying amount of hedged items	$ 10,325	$ 11,112
Active hedged asset adjustments	(1,552)	(1,320)
Discontinued hedged asset adjustments	(63)	(70)
Total hedged asset adjustments	$ (1,615)	$ (1,390)
Hedged Asset, Statement of Financial Position [Extensible Enumeration]	Securities available-for-sale (includes amortized cost of $28.0 billion at both March 31, 2024 and December 31, 2023, an allowance for credit losses of nil at both March 31, 2024 and December 31, 2023, and $863 million and $161 million pledged to creditors at March 31, 2024 and December 31, 2023, respectively)	Securities available-for-sale (includes amortized cost of $28.0 billion at both March 31, 2024 and December 31, 2023, an allowance for credit losses of nil at both March 31, 2024 and December 31, 2023, and $863 million and $161 million pledged to creditors at March 31, 2024 and December 31, 2023, respectively)
Deposits
Derivatives, Fair Value [Line Items]
Carrying amount of hedged liability items	$ 1,451	$ 1,463
Active hedged liability adjustments	(108)	(104)
Discontinued hedged liability adjustments	59	67
Total hedged liability adjustments	$ (49)	$ (37)
Hedged Liability, Statement of Financial Position [Extensible Enumeration]	Deposits	Deposits
Long-term debt
Derivatives, Fair Value [Line Items]
Carrying amount of hedged liability items	$ 8,864	$ 7,913
Active hedged liability adjustments	(448)	(407)
Discontinued hedged liability adjustments	63	72
Total hedged liability adjustments	$ (385)	$ (335)
Hedged Liability, Statement of Financial Position [Extensible Enumeration]	Long-term debt (includes $6.9 billion and $7.5 billion designated under fair value option at March 31, 2024 and December 31, 2023, respectively)	Long-term debt (includes $6.9 billion and $7.5 billion designated under fair value option at March 31, 2024 and December 31, 2023, respectively)