Changes in Stockholders' Equity (Schedule of Stockholders' Equity) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Jan. 01, 2018
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance beginning of period	$ 3,128.7	$ 2,998.1	$ 2,993.5	$ 3,095.3
Stock compensation	8.1	10.5	32.9	33.0
Issuance of stock awards	(0.1)	(0.1)	(23.0)	(3.1)
Net income (loss)		70.7		186.1
SSARs exercised	(0.7)		(4.1)	(0.4)
Net income	6.3	70.7	212.4	186.1
Net income (loss)	7.6	71.1	213.5	186.8
Other comprehensive loss, net of reclassification adjustments:
Foreign currency translation adjustments	(62.7)	(53.1)	(46.1)	(233.8)
Defined benefit pension plans, net of tax	2.8	2.9	8.8	9.0
Deferred gains and losses on derivatives, net of tax	(1.6)	0.9	(0.9)	1.5
Payment of dividends to stockholders	(12.2)	(11.8)	(35.9)	(35.6)
Purchases and retirement of common stock	(30.0)	(50.0)	(100.0)	(84.3)
Investment by noncontrolling interests	0.2	0.8	1.2	0.8
Balance end of period	3,038.8	2,968.9	3,038.8	2,968.9
Adjustment related to the adoption of ASU 2014-09					$ 0.4
Common Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance beginning of period	0.8	0.8	0.8	0.8
Other comprehensive loss, net of reclassification adjustments:
Balance end of period	0.8	0.8	0.8	0.8
Additional Paid-in Capital
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance beginning of period	7.1	121.4	10.2	136.6
Stock compensation	8.1	10.5	32.9	33.0
Issuance of stock awards		(0.1)	(13.2)	(3.1)
SSARs exercised			(3.1)	(0.4)
Other comprehensive loss, net of reclassification adjustments:
Purchases and retirement of common stock	(11.3)	(50.0)	(22.9)	(84.3)
Balance end of period	3.9	81.8	3.9	81.8
Retained Earnings
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance beginning of period	4,591.1	4,346.1	4,477.3	4,253.8
Issuance of stock awards	(0.1)		(9.8)
Net income (loss)		71.1		186.8
SSARs exercised	(0.7)		(1.0)
Net income	7.6		213.5
Other comprehensive loss, net of reclassification adjustments:
Payment of dividends to stockholders	(12.2)	(11.8)	(35.9)	(35.6)
Purchases and retirement of common stock	(18.7)	0.0	(77.1)	0.0
Balance end of period	4,567.0	4,405.4	4,567.0	4,405.4
Adjustment related to the adoption of ASU 2014-09					$ 0.4
Accumulated Other Comprehensive Loss
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance beginning of period	(1,534.3)	(1,533.5)	(1,555.4)	(1,361.6)
Other comprehensive loss, net of reclassification adjustments:
Foreign currency translation adjustments	(62.0)	(52.2)	(47.6)	(230.8)
Defined benefit pension plans, net of tax	2.8	2.9	8.8	9.0
Deferred gains and losses on derivatives, net of tax	(1.6)	0.9	(0.9)	1.5
Balance end of period	(1,595.1)	(1,581.9)	(1,595.1)	(1,581.9)
Noncontrolling Interests
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance beginning of period	64.0	63.3	60.6	65.7
Net income (loss)		(0.4)		(0.7)
Net income	(1.3)		(1.1)
Other comprehensive loss, net of reclassification adjustments:
Foreign currency translation adjustments	(0.7)	(0.9)	1.5	(3.0)
Investment by noncontrolling interests	0.2	0.8	1.2	0.8
Balance end of period	$ 62.2	$ 62.8	$ 62.2	$ 62.8