Shareholders' Equity - Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance			$ (25.3)
Total other comprehensive income, net of tax	$ 0.2	$ 0.8	0.4	$ 76.2
Ending balance	(19.5)		(19.5)
Amortization of net actuarial loss	7.0	8.7	23.4	27.6
Pension curtailment / settlement loss	1.2	1.3	1.1	7.1
Net loss including noncontrolling interest	(6.0)	7.1	10.4	103.8
Cumulative translation adjustment	0.0	0.0	0.0	(75.8)
Reclassification out of Accumulated Other Comprehensive Income
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Net loss including noncontrolling interest	0.2	0.5	0.4	78.8
Defined Benefit Plans
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance			(19.6)
Other comprehensive income (loss) before reclassifications, net of tax			(0.8)
Amounts reclassified from accumulated other comprehensive income, net of tax			1.1
Reclassification			(0.1)
Total other comprehensive income, net of tax			0.2
Ending balance	(19.4)		(19.4)
Defined Benefit Plans | Reclassification out of Accumulated Other Comprehensive Income
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Amortization of net actuarial loss	0.9	0.2	1.1	0.4
Pension curtailment / settlement loss	(0.8)	0.3	(0.8)	2.6
Net loss including noncontrolling interest	0.1	0.5	0.3	3.0
Foreign Currency Translation
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance			(1.0)
Other comprehensive income (loss) before reclassifications, net of tax			0.1
Amounts reclassified from accumulated other comprehensive income, net of tax			0.0
Reclassification			0.0
Total other comprehensive income, net of tax			0.1
Ending balance	(0.9)		(0.9)
Foreign Currency Translation | Reclassification out of Accumulated Other Comprehensive Income
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Cumulative translation adjustment	0.1	$ 0.0	0.1	$ 75.8
Total
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance			(20.6)
Other comprehensive income (loss) before reclassifications, net of tax			(0.7)
Amounts reclassified from accumulated other comprehensive income, net of tax			1.1
Reclassification			(0.1)
Total other comprehensive income, net of tax			0.3
Ending balance	$ (20.3)		$ (20.3)