Nonoperating Income (Expense) (Narrative) (Details) - USD ($) $ / shares in Units, $ in Millions |
1 Months Ended | 3 Months Ended | 12 Months Ended | ||
---|---|---|---|---|---|
Aug. 31, 2016 |
Sep. 30, 2016 |
Dec. 31, 2017 |
Dec. 31, 2016 |
Dec. 31, 2015 |
|
Other Income and Expenses [Abstract] | |||||
Proceeds from sales of marketable equity securities | $ 137.9 | $ 264.8 | $ 43.0 | ||
Increase in other receivables from sale of certain marketable securities | 22.0 | ||||
Gain on sale of marketable equity securities | 73.0 | 223.0 | 12.0 | ||
Marketable securities, after tax realized gain | $ 46.0 | $ 140.0 | $ 8.0 | ||
Marketable securities, after-tax gain, per diluted share | $ 0.06 | $ 0.20 | $ 0.01 | ||
Payments of debt extinguishment costs | $ 188.0 | $ 188.0 | $ 0.0 | $ 188.1 | $ 0.0 |
Loss on early extinguishment of borrowings | $ 0.0 | 178.8 | $ 0.0 | ||
Extinguishment of debt, gain (loss), net of tax | $ (112.0) | ||||
Extinguishment of borrowings, (loss), per share, new of tax | $ 0.16 |