CONDENSED 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 (loss)		$ (184.4)	$ 48.8	$ 183.0	$ (67.9)
Pension and other postretirement plans adjustments:
Amortization of prior service costs		0.0	0.0	0.0	0.1
Amortization of actuarial losses(1)	[1]	0.3		0.4	0.1
Net curtailment (1)	[2]		0.1		(0.3)
Other comprehensive income (loss)		0.3	0.1	0.4	(0.1)
Comprehensive income (loss)		$ (184.1)	$ 48.9	$ 183.4	$ (68.0)

[1] Presented net of income tax benefit of $0.1 million for the three and six months ended June 30, 2020.

[2] Presented net of income tax expense of $0.1 million for the six months ended June 30, 2019.