Investment Securities (Fair Value of Securities Pledged and Accepted as Collateral) (Details) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Summary of Investment Holdings [Line Items]
Permitted by contract or custom to sell or repledge	$ 819	$ 755
Permitted amount repledged to others	819	755
Asset Pledged as Collateral
Summary of Investment Holdings [Line Items]
Debt securities, pledged to others	$ 68,193	$ 29,878