Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical) - USD ($) shares in Millions, $ in Millions	Mar. 31, 2023	Dec. 31, 2022
Statement Of Financial Position [Abstract]
Accounts and accrued income receivable, allowances	$ 20.6	$ 21.3
Debt securities, amortized costs	8,478.2	9,169.6
Pledged securities included in debt securities	$ 91.0	$ 86.0
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	103.3	103.2