Income Taxes - Income Tax Reconciliation (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018		Dec. 31, 2017
Income Tax Disclosure [Abstract]
Tax Expense associated with the goodwill write-off as part of our asset divestiture		$ 2.9
Computed expected tax provision	$ (1.7)	(28.0)		$ 14.3
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Impairment Losses, Amount	0.0	41.0		0.0
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Amount	0.0	0.0		(70.1)
State and local taxes, net of federal income tax impact	(0.9)	4.4		(1.2)
Effective Income Tax Rate Reconciliation, Tax Contingency, State and Local, Amount	(1.2)	0.1		(0.7)
Effective Income Tax Rate Reconciliation, Tax Credit, Other, Amount	2.3	10.9		3.2
Uncertain tax positions	0.7	0.0		0.3
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Share-based Payment Arrangement, Amount	0.6	0.7		2.2
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Amount	0.4	0.2		0.3
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount	2.3	0.0		0.8
Other	(0.2)	2.8	[1]	0.9
Income tax provision	$ (2.3)	$ 10.3		$ (56.4)

[1] Includes $2.9 million of expense associated with the write-off of goodwill as part of our divestiture discussed in Note 10, "Other Operating Charges, net" for the year ended December 31, 2018.