Income Tax Matters, Reconciliation Between Income Tax Provision and Statutory Income Tax Provision Table (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Reconciliation between income tax provision and statutory income tax provision:
Amount of federal income tax provision based on the statutory rate	$ (16.9)	$ (25.2)	$ (46.5)
(Increase) decrease in federal valuation allowances	(0.1)	1.7	0.5
Non-deductible compensation expense	(1.7)	(0.6)	(2.3)
Non-deductible benefit (expense)	0.1	(1.5)	0.0
State income taxes, net of federal benefit	(4.5)	(2.5)	(4.3)
Research and development credit	7.7	0.0	0.0
Gross increases for tax positions from current year	(0.3)	0.0	0.0
Gross increases for tax positions from prior years	(2.4)	0.0	0.0
Foreign income tax expense	(0.1)	(0.5)	(0.1)
Foreign undistributed (earnings) loss	(0.2)	0.4	(5.9)
Tax rate change	0.0	0.1	29.0
Income tax provision	(18.4)	(28.3)	(87.6)
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Amount			(2.5)
State and Local Jurisdiction [Member]
Reconciliation between income tax provision and statutory income tax provision:
(Increase) decrease in federal valuation allowances	(1.4)	2.9	2.2
State and tax expense (benefit) before adjustments	3.8	4.5	$ 4.0
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Amount	$ 0.7	$ (0.9)