Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Net income	$ 80.3	$ (27.3)	$ 321.1	$ 93.9
Other comprehensive income
Foreign currency translation loss	(0.3)	0.0	(0.4)	0.0
Defined benefit pension and postretirement plans:
Net loss arising from remeasurement during the period, net of tax of $0.6	0.0	0.0	1.1	0.0
Amortization of prior service benefits, net of tax of ($1.3), ($1.4), ($4.1), ($4.2)	(2.6)	(2.4)	(7.4)	(7.2)
Amortization of net actuarial loss, net of tax of $2.3, $2.1, $8.5, $6.3	4.3	3.6	15.3	10.8
Reclassification adjustment for curtailment loss included in net income, net of tax of $0.1	0.0	0.0	0.2	0.0
Other comprehensive income	1.4	1.2	8.8	3.6
Total comprehensive income (loss)	$ 81.7	$ (26.1)	$ 329.9	$ 97.5