Regulatory Capital Matters - Schedule of actual and required capital amounts for the bank and ratios (Details) $ in Millions	Mar. 31, 2024 USD ($)	Dec. 31, 2023 USD ($)
Tier I capital (to average assets), Amount [Abstract]
Banking Regulation, Tier One Leverage Capital, Actual	$ 80,180	$ 79,101
To be well	$ 37,823	$ 37,384
Tier I capital (to average assets), Ratio [Abstract]
Community bank leverage ratio minimum requirement	0.1908	0.1904
To be well	0.09	0.09