Changes In Equity And Accumulated Other Comprehensive Loss (Summary Of Changes In Equity) (Detail) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended				6 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019
Changes In Equity And Comprehensive Income [Line Items]
Net Income (Loss) Attributable to Parent	$ 14.8	$ 62.8	$ 91.0		$ 77.6	$ 173.4
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period	1,407.5	1,476.3	1,593.0	$ 1,527.1	1,476.3	1,527.1
Net income	14.8	62.8	91.0	82.5	77.6	173.5
Net Income (Loss) Attributable to Noncontrolling Interest	0.0		0.0		0.0	(0.1)
Cash dividends	(24.9)	(25.5)	(23.3)	(23.4)
Stock-based compensation expense	4.7	5.8	5.6	5.5
Deconsolidation of a joint venture				(0.5)
Changes in pension and postretirement plan assets and benefit obligation, net of tax	3.6	3.6	1.9	2.9	7.1	4.8
Currency translation adjustment	17.4	(45.5)	4.7	(0.9)
Balance, end of period	1,423.6	1,407.5	1,674.4	1,593.0	$ 1,423.6	$ 1,674.4
Impact from settlement of share-based awards, net of shares acquired	$ 0.5	0.0	$ 1.5	$ (0.2)
Stock Repurchased During Period, Value		$ (70.0)
Dividends per share (in dollars per share)	$ 0.43	$ 0.43	$ 0.39	$ 0.39	$ 0.86	$ 0.78
Common Shares Issued At Par Value [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period	$ 72.4	$ 72.4	$ 72.4	$ 72.4	$ 72.4	$ 72.4
Balance, end of period	72.4	72.4	72.4	72.4	72.4	72.4
Additional Paid-in Capital
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period	315.4	315.6	299.2	303.5	315.6	303.5
Stock-based compensation expense	4.7	5.8	5.6	5.5
Balance, end of period	318.7	315.4	304.1	299.2	318.7	304.1
Impact from settlement of share-based awards, net of shares acquired	(1.4)	(6.0)	(0.7)	(9.8)
Retained Earnings
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period	2,149.5	2,112.2	2,131.1	2,072.1	2,112.2	2,072.1
Net income			91.0	82.4
Cash dividends	(24.9)	(25.5)	(23.3)	(23.4)
Balance, end of period	2,139.4	2,149.5	2,198.8	2,131.1	2,139.4	2,198.8
AOCI Attributable to Parent
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period	(525.3)	(483.7)	(445.5)	(447.6)	(483.7)	(447.6)
Changes in pension and postretirement plan assets and benefit obligation, net of tax	3.6	3.6	1.9	2.9
Currency translation adjustment	17.2	(45.2)	4.7	(0.8)
Balance, end of period	(504.5)	(525.3)	(438.9)	(445.5)	(504.5)	(438.9)
Treasury Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period	(606.8)	(542.8)	(466.6)	(476.2)	(542.8)	(476.2)
Balance, end of period	(604.9)	(606.8)	(464.4)	(466.6)	(604.9)	(464.4)
Impact from settlement of share-based awards, net of shares acquired	1.9	6.0	2.2	9.6
Stock Repurchased During Period, Value		(70.0)
Parent
Changes In Equity And Comprehensive Income [Line Items]
Net Income (Loss) Attributable to Parent	14.8	62.8	91.0	82.4
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period	1,405.2	1,473.7	1,590.6	1,524.2	1,473.7	1,524.2
Cash dividends	(24.9)	(25.5)	(23.3)	(23.4)
Stock-based compensation expense	4.7	5.8	5.6	5.5
Changes in pension and postretirement plan assets and benefit obligation, net of tax	3.6	3.6	1.9	2.9
Currency translation adjustment	17.2	(45.2)	4.7	(0.8)
Balance, end of period	1,421.1	1,405.2	1,672.0	1,590.6	1,421.1	1,672.0
Impact from settlement of share-based awards, net of shares acquired	0.5	0.0	1.5	(0.2)
Stock Repurchased During Period, Value		(70.0)
Noncontrolling Interest
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period	2.3	2.6	2.4	2.9	2.6	2.9
Net Income (Loss) Attributable to Noncontrolling Interest	0.0	0.0	0.0	(0.1)
Deconsolidation of a joint venture				(0.5)
Currency translation adjustment	0.2	(0.3)	0.0	(0.1)
Balance, end of period	$ 2.5	$ 2.3	$ 2.4	$ 2.4	$ 2.5	$ 2.4