Consolidated Statements of Comprehensive Income (Loss) - 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	$ 168.9	$ 32.7	$ 258.2	$ 38.0
Interest rate swap:
Realized gain (loss)	(0.2)	0.0	(0.1)	0.0
Unrealized gain (loss)	(0.6)	0.0	(4.2)	0.0
Reclassified to interest expense	0.2	0.0	0.1	0.0
Total	(0.6)	0.0	(4.2)	0.0
Deferred income tax (benefit) expense	(0.1)	0.0	(1.0)	0.0
Other comprehensive income (loss)	(0.5)	0.0	(3.2)	0.0
Comprehensive income	$ 168.4	$ 32.7	$ 255.0	$ 38.0