Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical) - USD ($) shares in Millions, $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Statement of Financial Position [Abstract]
Accounts and accrued income receivable, allowances	$ 22.8	$ 21.8
Pledged securities included in debt securities	98.5	107.0
Debt securities, amortized cost	$ 7,256.7	$ 7,895.2
Preferred stock, par value	$ 0.00001	$ 0.00001
Preferred stock, shares authorized	0.5	0.5
Preferred stock, outstanding	0.0	0.0
Common stock, par value	$ 0.00001	$ 0.00001
Common stock, shares authorized	300.0	300.0
Common stock, shares outstanding	103.0	103.1