CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Unaudited) - USD ($) $ in Millions	3 Months Ended				6 Months Ended
	Jun. 30, 2019		Jun. 30, 2018		Jun. 30, 2019		Jun. 30, 2018
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 48.8		$ (336.0)		$ (67.9)		$ (389.6)
Fair value of plan assets adjustment(1)	0.0		0.0		0.0		0.3	[1]
Pension and other postretirement plans adjustments:
Amortization of prior service costs(2)	0.0		0.1	[2]	0.1		0.2	[2]
Amortization of actuarial losses(3)	0.0		0.2	[3]	0.1		0.4	[3]
Curtailment Gain (Loss), after Tax(4)	0.1	[4]	0.0		(0.3)	[4]	0.0
Other comprehensive income (loss)	0.1		0.3		(0.1)		0.9
Comprehensive income (loss)	$ 48.9		$ (335.7)		$ (68.0)		$ (388.7)

[1] Adjustment recorded during the six months ended June 30, 2018, related to a change in the fair value of plan assets as of December 31, 2017.

[2] Presented net of income tax expense of $0.1 million and $0.1 million for the three and six months ended June 30, 2018, respectively.

[3] Presented net of income tax expense of $0.1 million and $0.2 million for the three and six months ended June 30, 2018, respectively.

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