CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY - USD ($) shares in Millions, $ in Millions	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Retained Earnings	Treasury Stock at Cost	Non-controlling Interests
Beginning Balance (in shares) at Dec. 31, 2016		58.5
Beginning Balance at Dec. 31, 2016	$ 4,426.5	$ 0.6	$ 1,073.5	$ (122.9)	$ 3,054.4	$ (386.0)	$ 806.9
Increase (Decrease) in Stockholders' Equity
Net income	398.0				248.8		149.2
Other comprehensive income	39.1			28.5			10.6
Share-based compensation	19.7		19.7
Common stock issued under share-based incentive plans	10.3		(79.1)			89.4
Share repurchases	(202.2)					(202.2)
Dividends ($0.40 per share and $0.60 per share)	(22.9)				(22.9)
Issuance costs and other	0.3		0.3
Affiliate equity activity:
Affiliate equity expense	28.5		7.1				21.4
Issuances	2.3		(0.2)				2.5
Repurchases	33.8		33.8
Changes in redemption value of Redeemable non-controlling interests	(142.8)		(142.8)
Transfers to Redeemable non-controlling interests	(47.2)						(47.2)
Capital contributions by Affiliate equity holders	5.6						5.6
Distributions to non-controlling interests	(178.6)						(178.6)
Ending Balance (in shares) at Jun. 30, 2017		58.5
Ending Balance at Jun. 30, 2017	$ 4,370.4	$ 0.6	912.3	(94.4)	3,280.3	(498.8)	770.4
Beginning Balance (in shares) at Dec. 31, 2017	58.5	58.5
Beginning Balance at Dec. 31, 2017	$ 4,578.5	$ 0.6	808.6	(21.8)	3,698.5	(663.7)	756.3
Increase (Decrease) in Stockholders' Equity
Net income	429.3				270.0		159.3
Other comprehensive income	9.2			15.1			(5.9)
Share-based compensation	21.8		21.8
Common stock issued under share-based incentive plans	(8.8)		(3.5)			(5.3)
Share repurchases	(300.8)					(300.8)
Dividends ($0.40 per share and $0.60 per share)	(33.0)				(33.0)
Affiliate equity activity:
Affiliate equity expense	27.7		4.8				22.9
Issuances	7.0		(4.8)				11.8
Repurchases	14.1		14.1
Changes in redemption value of Redeemable non-controlling interests	(161.3)		(161.3)
Transfers to Redeemable non-controlling interests	(23.4)						(23.4)
Capital contributions by Affiliate equity holders	2.4						2.4
Distributions to non-controlling interests	$ (205.3)						(205.3)
Ending Balance (in shares) at Jun. 30, 2018	58.5	58.5
Ending Balance at Jun. 30, 2018	$ 4,357.4	$ 0.6	$ 679.7	$ (6.7)	$ 3,935.5	$ (969.8)	$ 718.1