Income Taxes - Schedule of Deferred Income Taxes (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Assets
Net operating loss carryforwards	$ 67.8	$ 65.1
Unfunded pension liability and other postretirement obligations	1.7	0.5
ASC 606 - revenue from contracts with customers	9.3
Tax credit carryforwards	8.1	10.8
Stock based compensation	8.4	7.1
Other comprehensive income	4.1	0.2
Reserves and other	15.6	13.5
Subtotal	115.0	97.2
Valuation allowance	(48.8)	(54.9)
Total assets	66.2	42.3
Liabilities
Accelerated depreciation	(163.0)	(144.1)
Accelerated amortization	(11.8)	(11.3)
Other	(4.0)	(1.3)
Total liabilities	(178.8)	(156.7)
Net deferred tax (liabilities) assets	$ (112.6)	$ (114.4)