Nature Of Operations And Significant Accounting Policies (Computation Of Basic And Diluted Earnings Per Share) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accounting Policies [Abstract]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount									0.4	0.9	1.1
Less: Noncontrolling interest in subsidiaries’ earnings									$ 0.7	$ 1.0	$ 1.1
Net income attributable to common shareholders	$ (28.7)	$ 68.2	$ 69.2	$ 63.1					$ 171.8	$ 122.8	$ 228.9
Weighted average basic shares outstanding									59.4	58.5	58.1
Effect of dilutive stock options									1.0	0.8	0.7
Average diluted shares outstanding									60.4	59.3	58.8
Earnings per share - diluted:
Earnings Per Share, Basic	$ (0.48)	$ 1.15	$ 1.16	$ 1.06	$ (1.11)	$ 1.09	$ 1.17	$ 0.95	$ 2.89	$ 2.10	$ 3.94
Earnings Per Share, Diluted	$ (0.48)	$ 1.13	$ 1.14	$ 1.05	$ (1.08)	$ 1.07	$ 1.15	$ 0.93	$ 2.84	$ 2.07	$ 3.89