Statement of Consolidated Comprehensive Income (Loss) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 20.2	$ (10.8)	$ 21.5
Other Comprehensive (Income) Loss, Defined Benefit Plan, before Reclassification Adjustment, after Tax [Abstract]
Net actuarial gains (losses) and other adjustments	1.0	36.1	(69.5)
Net prior service credit	0.0	8.9	0.0
Settlement adjustment	10.9	6.3	0.0
Amortization of prior net losses	14.6	12.9	13.7
Amortization of prior net service credit	(0.4)	0.0	0.0
Changes in foreign currency translation adjustments	(2.6)	5.2	1.3
Reclassification of foreign currency translation gains to net income	0.0	0.0	(10.4)
Other comprehensive income (loss)	23.5	69.4	(64.9)
Comprehensive income (loss)	$ 43.7	$ 58.6	$ (43.4)