Derivative Instruments - Pre-tax Portion of the Fair Value of Foreign Currency Forward Contracts and Foreign Currency Options (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Unrealized gains	$ 17.9	$ 50.6
Unrealized (losses)	(153.1)	(0.3)
Net unrealized gains (losses)	$ (135.2)	$ 50.3

The net change in the difference between the fair value and the carrying value, or in the comparative fair values, of derivative instruments, including options, swaps, futures, and forward contracts, held at each balance sheet date, that was included in earnings for the period.