Income Tax Matters, Reconciliation of Changes in the Gross Unrecognized Tax Benefits Table (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Unrecognized Tax Benefits, Increase Resulting from Current Period Tax Positions	$ 0.3
Reconciliation of changes in the gross unrecognized tax benefits:
Gross unrecognized tax benefits at beginning of period	1.5	$ 1.5	$ 1.8
Gross increases for tax positions of prior years	2.3	0.0	0.0
Gross decreases for tax positions of prior years	0.0	0.0	(0.3)
Gross unrecognized tax benefits at end of period	$ 4.1	$ 1.5	$ 1.5