Investment Securities - Rollforward of Fair Value Measurements by Level (Details) - Other long-term investments - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ 1,138.2	$ 911.6
Net realized and unrealized gains	54.4	157.3
Purchases and contributions	111.5	256.6
Sales and distributions	(41.4)	(187.3)
Transfers in	0.0	0.0
Transfers out	0.0	0.0
Ending balance	$ 1,262.7	$ 1,138.2