Nonoperating Income (Expense) (Narrative) (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Other Income and Expenses [Abstract]
Other nonoperating income, net pension and postretirement benefits	$ 37.0	$ (31.0)	$ (16.0)
Proceeds from sales of investments	22.2	137.9	264.8
Receivable from sale of marketable securities		22.0
Marketable securities, realized gain		73.0	223.0
Marketable securities, after tax realized gain		$ 46.0	$ 140.0
Marketable securities, after-tax gain, per diluted share		$ 0.06	$ 0.20
Payments of debt extinguishment costs	0.0	$ 0.0	$ 188.1
Loss on early extinguishment of borrowings	$ 0.0	$ 0.0	(178.8)
Extinguishment of debt, gain, net of tax			$ (112.0)
Extinguishment of debt, gain, per share, net of tax			$ (0.16)