Statements of Consolidated Comprehensive Income (Loss) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Net income (loss)	$ 45.4	$ 91.7	$ (236.6)
Other comprehensive (loss) income, net of tax – Note 10:
Defined benefit pension plan and VEBAs	(1.4)	(5.8)	65.1
Available for sale securities	0.5	0.9	(0.3)
Other	0.9	(0.1)	(0.4)
Other comprehensive (loss) income, net of tax	0.0	(5.0)	64.4
Comprehensive income (loss)	$ 45.4	$ 86.7	$ (172.2)