Investment Securities - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Available-for-sale, Realized Loss	$ (23.5)	$ (46.8)	$ (2.1)
Debt Securities, Available-for-sale, Realized Gain	0.0	$ 0.3	$ 3.2
Debt Securities, Held-to-maturity, Nonaccrual	0.0
Debt Securities, Current	853.0
Investment Securities, Primarily Classified As Available-For-Sale, Debt Maturities, Rolling Year Two Through Five, Amortized Cost Basis	1,603.3
Investment Securities, Primarily Classified As Available-For-Sale, Debt Maturities, Rolling Year Two Through Five, Fair Value	1,552.2
Collateral
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities	$ 0.0