Statements of Consolidated Comprehensive Income - 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 loss	$ 22.1	$ 15.9	$ (249.9)	$ 56.2
Reclassification adjustments:
Amortization of net actuarial loss (gain)	0.3	(0.5)	0.8	(1.4)
Amortization of prior service cost	0.7	2.6	2.2	8.0
Removal of obligation relating to Union VEBA	0.0	0.0	106.6	0.0
Other comprehensive income relating to VEBAs	1.0	2.1	109.6	6.6
Available for sale securities:
Unrealized (loss) gain on available for sale securities	(0.4)	(0.2)	(0.7)	0.1
Reclassification adjustments:
Reclassification of unrealized (gain) loss upon sale of available for sale securities	(0.1)	0.0	0.1	(0.2)
Other comprehensive loss relating to available for sale securities	(0.5)	(0.2)	(0.6)	(0.1)
Unrealized loss on foreign currency cash flow hedges	0.0	0.0	(0.2)	0.0
Foreign currency translation (loss) gain	(0.3)	0.1	(0.2)	0.2
Other comprehensive income, before tax	0.2	2.0	108.6	6.7
Income tax expense related to items of other comprehensive income	(0.1)	(0.7)	(41.2)	(2.4)
Other comprehensive income, net of tax	0.1	1.3	67.4	4.3
Comprehensive income (loss)	$ 22.2	$ 17.2	$ (182.5)	$ 60.5