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, 2021	Mar. 31, 2021	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2021	Jun. 30, 2020
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period	$ 1,598.0	$ 1,531.1	$ 1,407.5	$ 1,476.3	$ 1,531.1	$ 1,476.3
Net income	138.3	108.4	14.8	62.8	246.7	77.6
Cash dividends	(25.2)	(25.0)	(24.9)	(25.5)
Reacquisition on open market				(70.0)
Stock-based compensation expense	6.1	6.3	4.7	5.8
Changes in pension and postretirement plan assets and benefit obligation, net of tax	5.2	4.9	3.6	3.6	10.1	7.1
Currency translation adjustment	7.6	(34.9)	17.4	(45.5)
Balance, end of period	1,728.1	1,598.0	1,423.6	1,407.5	$ 1,728.1	$ 1,423.6
Impact from settlement of share-based awards, net of shares acquired	$ (1.9)	$ 7.2	$ 0.5	$ 0.0
Dividends per share (in dollars per share)	$ 0.43	$ 0.43	$ 0.43	$ 0.43	$ 0.86	$ 0.86
Reacquisition on open market (in shares)				1,221,233
Common Shares Issued at Par Value
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
Capital Surplus
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period	334.7	330.7	315.4	315.6	330.7	315.6
Stock-based compensation expense	6.1	6.3	4.7	5.8
Balance, end of period	348.4	334.7	318.7	315.4	348.4	318.7
Impact from settlement of share-based awards, net of shares acquired	7.6	(2.3)	(1.4)	(6.0)
Retained Earnings
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period	2,276.2	2,192.8	2,149.5	2,112.2	2,192.8	2,112.2
Net income	138.3	108.4	14.8	62.8
Cash dividends	(25.2)	(25.0)	(24.9)	(25.5)
Balance, end of period	2,389.3	2,276.2	2,139.4	2,149.5	2,389.3	2,139.4
Accumulated Other Comprehensive Loss
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period	(497.2)	(466.4)	(525.3)	(483.7)	(466.4)	(483.7)
Changes in pension and postretirement plan assets and benefit obligation, net of tax	5.2	4.9	3.6	3.6
Currency translation adjustment	7.7	(35.7)	17.2	(45.2)
Balance, end of period	(484.3)	(497.2)	(504.5)	(525.3)	(484.3)	(504.5)
Treasury Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period	(591.1)	(600.6)	(606.8)	(542.8)	(600.6)	(542.8)
Reacquisition on open market				(70.0)
Balance, end of period	(600.6)	(591.1)	(604.9)	(606.8)	(600.6)	(604.9)
Impact from settlement of share-based awards, net of shares acquired	(9.5)	9.5	1.9	6.0
Total Share- holders’ Equity
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period	1,595.0	1,528.9	1,405.2	1,473.7	1,528.9	1,473.7
Net income	138.3	108.4	14.8	62.8
Cash dividends	(25.2)	(25.0)	(24.9)	(25.5)
Reacquisition on open market				(70.0)
Stock-based compensation expense	6.1	6.3	4.7	5.8
Changes in pension and postretirement plan assets and benefit obligation, net of tax	5.2	4.9	3.6	3.6
Currency translation adjustment	7.7	(35.7)	17.2	(45.2)
Balance, end of period	1,725.2	1,595.0	1,421.1	1,405.2	1,725.2	1,421.1
Impact from settlement of share-based awards, net of shares acquired	(1.9)	7.2	0.5	0.0
Non-controlling Interest
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period	3.0	2.2	2.3	2.6	2.2	2.6
Net income	0.0	0.0	0.0	0.0
Currency translation adjustment	(0.1)	0.8	0.2	(0.3)
Balance, end of period	$ 2.9	$ 3.0	$ 2.5	$ 2.3	$ 2.9	$ 2.5