CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Millions	Sep. 30, 2025	Dec. 31, 2024
Statement of Financial Position [Abstract]
Fixed maturities available-for-sale, amortized cost	$ 679.3	$ 607.1
Short-term investments, cost	23.5	27.5
Premium receivable, allowance for doubtful accounts	$ 3.1	$ 2.8
Common stock, par value (usd per share)	$ 0.00001	$ 0.00001
Common stock, authorized (in shares)	200,000,000	200,000,000
Common stock, issued (in shares)	74,665,921	72,720,866
Common stock, outstanding (in shares)	74,665,921	72,720,866