Leases, Premises and Equipment - Supplemental Balance Sheet Information (Details) - USD ($) $ in Millions	Sep. 30, 2025	Dec. 31, 2024
Operating Leases:
Operating lease right-of-use assets	$ 389	$ 416
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration]	Other assets	Other assets
Operating lease liabilities	$ 438	$ 463
Operating Lease, Liability, Statement of Financial Position [Extensible Enumeration]	Operating lease liabilities	Operating lease liabilities
Weighted average remaining lease term	10 years 3 months 18 days	10 years 8 months 12 days
Weighted average discount rate %	4.79%	4.77%