Regulatory Matters (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2024	Mar. 31, 2024	Dec. 31, 2023
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Amount available for dividend payments to parent company without prior regulatory approval	$ 7,400
Outstanding cash reserves at the Federal Reserve Bank	39,000
FDIC-Related Assessments
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Loss contingency	$ (18)	$ 130	$ 515