Income Taxes - Net Deferred Income Tax Asset (Liability) (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Deferred income tax asset (liability):
Depreciation and amortization	$ (371.2)	$ (457.8)
Inventory basis differences	27.8	21.3
Accrued liabilities	87.1	87.9
Allowance for doubtful accounts	3.0	1.5
R&D	58.8	58.9
Loss and credit carryforwards	359.2	292.5
Share-based compensation	19.6	16.2
Federal benefit of unrecognized tax positions	18.2	17.0
Interest carryforwards	76.1	30.5
Unremitted earnings	(8.3)	(9.3)
Other, net	6.5	37.5
Subtotal	276.8	96.2
Valuation allowance (1)	(557.9)	(407.7)
Net deferred income tax liability:	(281.1)	(311.5)
Deferred income tax assets	1.2	10.4
Deferred income tax liabilities	$ (282.3)	$ (321.9)