Long-Term Debt And Notes Payable (Capitalization Of Long-Term Debt) (Details) $ in Millions	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Debt Disclosure [Abstract]
Current maturities of long-term debt	$ 249.4	$ 0.0
Long-term debt	494.1	745.3
Total indebtedness	743.5
Total shareholders' equity	1,345.2	$ 1,133.8
Capitalization	$ 2,088.7
Total indebtedness to capitalization	0.36