Investment Securities - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
	Sep. 30, 2025	Mar. 31, 2025	Dec. 31, 2024	Sep. 30, 2024
Investments, Debt and Equity Securities [Abstract]
Investment securities transferred from AFS to HTM	$ 44,100
Unrealized gains included in AOCI for investment securities transferred from AFS to HTM	$ 575
Approximate percentage rated at least AA+	99.00%		99.00%
Investment securities, allowance for credit losses	$ 105		$ 152	$ 175
Corporate debt securities
Debt Securities, Available-for-sale [Line Items]
Securities sold		$ 17