Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Statement of Comprehensive Income [Abstract]
Net income	$ 96.4	$ 164.4	$ 12.6	$ 328.8
Other comprehensive income, net of tax:
Unrealized gain on securities, net of tax	1.2	0.5	1.1	1.1
Other comprehensive income	1.2	0.5	1.1	1.1
Comprehensive income	$ 97.6	$ 164.9	$ 13.7	$ 329.9