CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Unaudited) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Statement of Comprehensive Income [Abstract]
Net income (loss)		$ 21.1	$ 171.1	$ (110.8)	$ 118.5
Pension and other postretirement plans adjustments:
Amortization of net actuarial loss	[1]		0.2	0.2	0.4
Amortization of prior service cost	[2]	0.3	0.7	0.9	2.4
Other comprehensive income		0.3	0.9	1.1	2.8
Comprehensive income (loss)		$ 21.4	$ 172.0	$ (109.7)	$ 121.3

[1] Presented net of income tax expense of $0.2 million during the nine months ended September 30, 2015, and $0.2 million during the nine months ended September 30, 2014.

[2] Presented net of income tax expense of $0.1 million and $0.5 million during the three and nine months ended September 30, 2015, respectively, and $0.5 million and $1.5 million during the three and nine months ended September 30, 2014, respectively.