CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY - USD ($) $ in Millions	Common stock	Additional paid-in-capital	Treasury shares	Accumulated other comprehensive loss	Retained earnings	Nonredeemable noncontrolling interests	Total
Balance at Dec. 31, 2018	$ 294.6	$ 3,824.5	$ (170.8)	$ (423.5)	$ 1,314.5	$ 21.5	$ 4,860.8
Balance (in shares) at Dec. 31, 2018	196,400,000
Increase (Decrease) in Stockholders' Equity
Net loss (income)					203.5	1.4	204.9
Other comprehensive loss				(0.5)			(0.5)
Dividends paid to shareholders		0.1			(138.4)		(138.3)
Share buyback program	$ (7.1)				(99.0)		(106.1)
Share buyback program (in shares)	(4,800,000)
Distributions to noncontrolling interests						(0.5)	(0.5)
Fair value adjustments to redeemable noncontrolling interests					0.2		0.2
Purchase of common stock for stock-based compensation plans		(33.2)	(4.9)				(38.1)
Vesting of stock-based compensation plans		(27.9)	27.9
Stock-based compensation plan expense		38.1					38.1
Balance at Jun. 30, 2019	$ 287.5	3,801.6	(147.8)	(424.0)	1,280.8	22.4	4,820.5
Balance (in shares) at Jun. 30, 2019	191,600,000
Balance at Mar. 31, 2019	$ 292.7	3,802.1	(165.4)	(386.8)	1,309.9	22.6	4,875.1
Balance (in shares) at Mar. 31, 2019	195,200,000
Increase (Decrease) in Stockholders' Equity
Net loss (income)					109.4	0.2	109.6
Other comprehensive loss				(37.2)			(37.2)
Dividends paid to shareholders		0.1			(68.7)		(68.6)
Share buyback program	$ (5.2)				(70.0)		(75.2)
Share buyback program (in shares)	(3,600,000)
Distributions to noncontrolling interests						(0.4)	(0.4)
Fair value adjustments to redeemable noncontrolling interests					0.2		0.2
Purchase of common stock for stock-based compensation plans		(1.8)	0.8				(1.0)
Vesting of stock-based compensation plans		(16.8)	16.8
Stock-based compensation plan expense		18.0					18.0
Balance at Jun. 30, 2019	$ 287.5	3,801.6	(147.8)	(424.0)	1,280.8	22.4	4,820.5
Balance (in shares) at Jun. 30, 2019	191,600,000
Balance at Dec. 31, 2019	$ 280.5	3,828.5	(139.5)	(367.1)	1,284.1	19.7	$ 4,906.2
Balance (in shares) at Dec. 31, 2019	187,000,000.0						186,975,693
Increase (Decrease) in Stockholders' Equity
Net loss (income)					(144.1)	(1.1)	$ (145.2)
Other comprehensive loss				(134.6)			(134.6)
Dividends paid to shareholders		0.1			(132.7)		(132.6)
Share buyback program	$ (4.7)				(48.5)		(53.2)
Share buyback program (in shares)	(3,100,000)
Distributions to noncontrolling interests						(0.5)	(0.5)
Fair value adjustments to redeemable noncontrolling interests					0.4		0.4
Purchase of common stock for stock-based compensation plans		(42.8)	(2.9)				(45.7)
Vesting of stock-based compensation plans		(27.8)	27.8
Stock-based compensation plan expense		34.1					34.1
Balance at Jun. 30, 2020	$ 275.8	3,792.1	(114.6)	(501.7)	959.2	18.1	$ 4,428.9
Balance (in shares) at Jun. 30, 2020	183,900,000						183,852,855
Balance at Mar. 31, 2020	$ 277.4	3,803.7	(137.9)	(511.0)	942.8	18.4	$ 4,393.4
Balance (in shares) at Mar. 31, 2020	184,900,000
Increase (Decrease) in Stockholders' Equity
Net loss (income)					102.9	0.1	103.0
Other comprehensive loss				9.3			9.3
Dividends paid to shareholders		0.1			(66.5)		(66.4)
Share buyback program	$ (1.6)				(20.4)		(22.0)
Share buyback program (in shares)	(1,000,000.0)
Distributions to noncontrolling interests						(0.4)	(0.4)
Fair value adjustments to redeemable noncontrolling interests					0.4		0.4
Purchase of common stock for stock-based compensation plans		(5.8)	(0.1)				(5.9)
Vesting of stock-based compensation plans		(23.4)	23.4
Stock-based compensation plan expense		17.5					17.5
Balance at Jun. 30, 2020	$ 275.8	$ 3,792.1	$ (114.6)	$ (501.7)	$ 959.2	$ 18.1	$ 4,428.9
Balance (in shares) at Jun. 30, 2020	183,900,000						183,852,855