Income Taxes - Detail of Deferred Tax Assets and Liabilities (Details 2) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Deferred tax assets:
Net operating and capital loss and tax credit carryforwards	$ 619.5	$ 835.2
Postretirement benefits	92.5	142.6
Pension benefits	117.5	260.3
Inventories	98.8	127.2
Other assets	71.6	125.1
Valuation allowance	(727.7)	(1,175.2)	$ (1,215.5)	$ (1,000.4)
Total deferred tax assets	272.2	315.2
Deferred tax liabilities:
Depreciable assets	(121.9)	(213.3)
Other liabilities	(111.4)	(48.7)
Total deferred tax liabilities	(233.3)	(262.0)
Net deferred tax assets	38.9	$ 53.2
Undistributed earnings of foreign subsidiaries	$ 0.0