Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Statement of Comprehensive Income [Abstract]
Net income	$ 22.2	$ 107.4	$ 121.7	$ 321.7
Other comprehensive gain (loss), net of tax:
Unrealized gain (loss) on securities, net of tax	(0.6)	(0.7)	0.2	(2.4)
Other comprehensive gain (loss)	(0.6)	(0.7)	0.2	(2.4)
Comprehensive income	$ 21.6	$ 106.7	$ 121.9	$ 319.3