Investment Securities - Held-To-Maturity Allowance For Credit Loss (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023	Mar. 31, 2024	Dec. 31, 2023	Mar. 31, 2023	Dec. 31, 2022
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Roll Forward]
Debt Securities, Held-to-maturity, Allowance for Credit Loss	$ 0.7	$ 0.7	$ 0.7	$ 0.7	$ 0.7	$ 0.8	$ 0.7	$ 1.9
Debt Securities, Held-to-Maturity, Credit Loss Expense (Reversal)	$ 0.0	$ 0.0	$ (0.1)	$ (1.2)