Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Deferred tax assets:
Accrued restructuring	$ 11.4	$ 12.6
Employee benefits	8.0	12.3
Intangibles	3.0	5.8
Investment in partnership	1.8	1.4
Net operating losses	9.0	5.4
Start-up costs	0.8	1.0
Inventory	1.2	0.0
Other	5.0	2.3
Total deferred tax assets	40.2	40.8
Valuation allowance	(20.4)	(18.8)
Total deferred tax assets, net of valuation allowance	19.8	22.0
Deferred tax liabilities:
Fixed assets	57.1	86.9
Other	0.0	(1.0)
Other	(0.6)	(0.5)
Total deferred tax liabilities	57.7	88.4
Net deferred tax liability	$ (37.9)	$ (66.4)