Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ (83.8)	$ 164.4
Other comprehensive income (loss), net of tax:
Unrealized gain (loss) on securities, net of tax	(0.1)	0.6
Other comprehensive income (loss)	(0.1)	0.6
Comprehensive income (loss)	$ (83.9)	$ 165.0