Investment Securities - Investment Gains and Losses For Level 3 (Details) - Other long-term investments - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Gain (Loss) on Securities [Line Items]
Total net unrealized investment gains recognized during the period on Level 3 investments held at the end of period	$ 180.2	$ 58.9	$ 195.2
Level 3
Gain (Loss) on Securities [Line Items]
Total net unrealized investment gains recognized during the period on Level 3 investments held at the end of period	$ 127.7	$ 57.2	$ 133.9