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	Non-Controlling Interests
Beginning balance (in shares) at Dec. 31, 2012	53.9
Beginning Balance at Dec. 31, 2012	$ 3,041.4	$ 0.5	$ 868.5	$ 79.1	$ 1,350.7	$ (214.6)	$ 957.2
Increase (Decrease) in Stockholders' Equity
Net income	669.6				360.5		309.1
Other comprehensive income (loss)	(7.1)			(5.1)			(2.0)
Share-based compensation	27.5		27.5
Common stock issued under share-based incentive plans	45.7		(53.2)			98.9
Tax benefit from share-based incentive plans	20.7		20.7
Settlement of senior convertible securities	(130.7)		(130.7)
Repurchases	(15.7)					(15.7)
Forward equity	(44.0)		(44.0)
Affiliate equity activity:
Affiliate equity expense	50.6		34.7				15.9
Issuances	11.0		(19.9)				30.9
Repurchases	(53.8)		(32.9)				(20.9)
Changes in Redemption value of Redeemable non-controlling interests	(190.8)		(190.8)
Transfers to Redeemable non-controlling interests	(19.5)						(19.5)
Capital Contributions by Affiliate equity holders	6.8						6.8
Distributions to non-controlling interests	$ (267.1)						(267.1)
Ending balance (in shares) at Dec. 31, 2013	53.9
Ending Balance at Dec. 31, 2013	$ 3,144.6	$ 0.5	479.9	74.0	1,711.2	(131.4)	1,010.4
Increase (Decrease) in Stockholders' Equity
Net income	785.6				452.1		333.5
Other comprehensive income (loss)	(58.3)			(42.2)			(16.1)
Share-based compensation	29.3		29.3
Common stock issued under share-based incentive plans	(5.3)		(134.4)			129.1
Tax benefit from share-based incentive plans	$ 60.2		60.2
Settlement of senior convertible securities (in shares)	1.9	1.9
Settlement of senior convertible securities	$ 276.5	$ 0.1	276.4
Repurchases	(238.6)					(238.6)
Forward equity	(45.0)		(45.0)
Investments in Affiliates	235.0						235.0
Affiliate equity activity:
Affiliate equity expense	66.2		29.2				37.0
Issuances	10.8						10.8
Repurchases	0.0		19.6				(19.6)
Changes in Redemption value of Redeemable non-controlling interests	(43.0)		(43.0)
Transfers to Redeemable non-controlling interests	(22.7)						(22.7)
Capital Contributions by Affiliate equity holders	17.3						17.3
Distributions to non-controlling interests	$ (569.4)						(569.4)
Ending balance (in shares) at Dec. 31, 2014	55.8
Ending Balance at Dec. 31, 2014	$ 3,643.2	0.6	672.2	31.8	2,163.3	(240.9)	1,016.2
Increase (Decrease) in Stockholders' Equity
Net income	833.7				516.0		317.7
Other comprehensive income (loss)	(69.2)			(49.9)			(19.3)
Share-based compensation	34.2		34.2
Common stock issued under share-based incentive plans	54.0		(131.0)			185.0
Tax benefit from share-based incentive plans	44.5		44.5
Repurchases	(366.0)					(366.0)
Forward equity	0.0
Investments in Affiliates	33.8						33.8
Affiliate equity activity:
Affiliate equity expense	62.0		10.4				51.6
Issuances	1.7		0.1				1.6
Repurchases	48.0		48.4				(0.4)
Changes in Redemption value of Redeemable non-controlling interests	(81.6)		(81.6)
Transfers to Redeemable non-controlling interests	(49.5)						(49.5)
Capital Contributions by Affiliate equity holders	11.7						11.7
Distributions to non-controlling interests	$ (431.4)						(431.4)
Ending balance (in shares) at Dec. 31, 2015	55.8
Ending Balance at Dec. 31, 2015	$ 3,769.1	$ 0.6	$ 597.2	$ (18.1)	$ 2,679.3	$ (421.9)	$ 932.0