Income Taxes Income Taxes (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Income Taxes [Abstract]
Deferred Tax Assets, Valuation Allowance	$ 5.8		$ 5.5
Excess tax benefits	$ 0.2	$ 2.5