Condensed Consolidated Statement of Changes in Stockholder's Equity - USD ($) $ in Millions	Common Stock	Treasury Stock	Additional Paid-In Capital	Retained Earnings	Accumulated Other Comprehensive Income, net	Redeemable Noncontrolling Interests	Total
Beginning balance at Dec. 31, 2017	$ 1.2	$ (558.3)	$ 2,623.7	$ 993.3	$ 50.7	$ 9.4	$ 3,110.6
Increase (Decrease) in Stockholders' Equity
Cash dividends on common stock				(30.6)			(30.6)
Stock-based compensation			11.0				11.0
Common stock repurchased from employee stock plans		(59.3)	0.6				(58.7)
Net income excluding noncontrolling interest				118.4			118.4
Other comprehensive income					24.8		24.8
Net loss attributable to redeemable noncontrolling interest						(0.3)
Redemption value adjustment of redeemable noncontrolling interest				(0.3)		0.3	(0.3)
Ending balance at Mar. 31, 2018	1.2	(617.6)	2,635.3	1,080.8	75.5	9.4	3,175.2
Beginning balance at Dec. 31, 2017	1.2	(558.3)	2,623.7	993.3	50.7	9.4	3,110.6
Increase (Decrease) in Stockholders' Equity
Net income excluding noncontrolling interest							201.7
Ending balance at Jun. 30, 2018	1.2	(665.9)	2,646.1	1,134.0	34.2	9.4	3,149.6
Beginning balance at Mar. 31, 2018	1.2	(617.6)	2,635.3	1,080.8	75.5	9.4	3,175.2
Increase (Decrease) in Stockholders' Equity
Cash dividends on common stock				(30.4)			(30.4)
Stock-based compensation			10.0				10.0
Common stock repurchased from employee stock plans		43.5	0.8				44.3
Purchase of common stock		(91.8)					(91.8)
Net income excluding noncontrolling interest				83.3			83.3
Other comprehensive income					(41.3)		(41.3)
Net loss attributable to redeemable noncontrolling interest				0.6		(0.3)	0.6
Redemption value adjustment of redeemable noncontrolling interest				(0.3)		0.3	(0.3)
Ending balance at Jun. 30, 2018	1.2	(665.9)	2,646.1	1,134.0	34.2	9.4	3,149.6
Beginning balance at Dec. 31, 2018	1.2	(720.1)	2,660.2	1,288.2	11.5	9.4	3,241.0
Increase (Decrease) in Stockholders' Equity
Cash dividends on common stock				(34.8)			(34.8)
Stock-based compensation			5.4				5.4
Exercise of common stock options			8.1				8.1
Common stock repurchased from employee stock plans		(10.0)					(10.0)
Purchase of common stock		(35.0)					(35.0)
Shares issued under employee stock purchase plan		0.8					0.8
Net income excluding noncontrolling interest				95.4			95.4
Other comprehensive income					14.7		14.7
Net loss attributable to redeemable noncontrolling interest						(0.2)
Redemption value adjustment of redeemable noncontrolling interest				(0.2)		0.2	(0.2)
Ending balance at Mar. 31, 2019	1.2	(764.3)	2,673.7	1,348.6	26.2	9.4	3,285.4
Beginning balance at Dec. 31, 2018	1.2	(720.1)	2,660.2	1,288.2	11.5	9.4	3,241.0
Increase (Decrease) in Stockholders' Equity
Net income excluding noncontrolling interest							182.6
Other comprehensive income					(3.4)
Net loss attributable to redeemable noncontrolling interest						(4.0)
Ending balance at Jun. 30, 2019	1.2	(764.6)	2,680.4	1,401.9	8.1	5.8	3,327.0
Beginning balance at Mar. 31, 2019	1.2	(764.3)	2,673.7	1,348.6	26.2	9.4	3,285.4
Increase (Decrease) in Stockholders' Equity
Cash dividends on common stock				(34.8)			(34.8)
Stock-based compensation			6.3				6.3
Exercise of common stock options			0.4				0.4
Common stock repurchased from employee stock plans		(0.4)					(0.4)
Shares issued under employee stock purchase plan		0.1					0.1
Net income excluding noncontrolling interest				88.3			88.3
Other comprehensive income					(18.1)		(18.1)
Net loss attributable to redeemable noncontrolling interest						(3.8)
Redemption value adjustment of redeemable noncontrolling interest				(0.2)		0.2	(0.2)
Ending balance at Jun. 30, 2019	$ 1.2	$ (764.6)	$ 2,680.4	$ 1,401.9	$ 8.1	$ 5.8	$ 3,327.0