Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Net income (loss)	$ 353.7	$ 75.6	$ (54.7)
Other comprehensive income (loss), net of tax:
Foreign currency translation loss	(0.4)	(0.1)	(0.1)
Defined benefit plans:
Net (loss) gain arising from remeasurement during the period, net of tax of ($3.4), ($25.0), $30.7	(6.6)	(45.4)	56.8
Net prior service credit, net of tax of $6.1	0.0	0.0	11.3
Amortization of prior service benefits included in net income (loss), net of tax of ($5.5), ($5.4), ($5.2)	(9.8)	(9.8)	(8.7)
Amortization of net actuarial loss included in net income (loss), net of tax of $10.8, $8.0, $10.1	19.5	14.7	17.5
Reclassification adjustment for curtailment loss (gain) included in net income (loss), net of tax of $0.1, ($0.2)	0.2	0.0	(0.4)
Total other comprehensive income (loss), net of tax	2.9	(40.6)	76.4
Total comprehensive income	$ 356.6	$ 35.0	$ 21.7