Changes In Equity And Comprehensive Income (Summary Of Changes In Equity) (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period			$ 1,348.5	$ 1,145.7
Dividends			(41.8)	(39.3)
Treasury Stock, Value, Acquired, Cost Method			25.0	0.0
Exercise of stock options, net of shares reacquired			5.0	17.8
Stock compensation expense			11.2	11.1
Excess tax benefit from stock based compensation				0.0
Net income	$ 80.7	$ 69.3	149.4	132.6
Other comprehensive income (loss)	(42.4)	38.7	(7.4)	63.2
Comprehensive income	38.3	108.0	142.0	195.8
Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest	(0.2)	0.3	(0.2)	0.7
Balance, end of period	1,446.6	1,331.1	1,446.6	1,331.1
Parent [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period			1,345.2	1,133.8
Dividends			(41.8)	(39.3)
Treasury Stock, Value, Acquired, Cost Method			25.0	0.0
Exercise of stock options, net of shares reacquired			5.0	17.8
Stock compensation expense			11.2	11.1
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets	6.7		6.7
Excess tax benefit from stock based compensation				0.0
Net income			149.4	132.3
Other comprehensive income (loss)			(7.2)	62.8
Comprehensive income			142.2	195.1
Balance, end of period	1,443.5	1,318.5	1,443.5	1,318.5
Noncontrolling Interest
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period			3.3	11.9
Net income			0.0	0.3
Other comprehensive income (loss)			(0.2)	0.4
Comprehensive income				0.7
Balance, end of period	$ 3.1	$ 12.6	$ 3.1	$ 12.6