CONSOLIDATED STATEMENTS OF CHANGES IN OWNERS' EQUITY AND SERIES A PREFERRED STOCK (Unaudited) - USD ($) shares in Thousands, $ in Millions	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings (Accumulated Deficit) [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Treasury Shares [Member]	Noncontrolling Interests [Member]	Series A Preferred Stock [Member]
Balance at Dec. 31, 2018	$ 7,470.8	$ 0.2	$ 6,154.9	$ (130.4)	$ 94.3	$ (39.6)	$ 1,391.4
Balance (in shares) at Dec. 31, 2018		231,791				666
Series A Preferred Stock at Dec. 31, 2018								$ 245.7
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Compensation on equity grants	32.7		32.7
Distribution equivalent rights	(6.9)		(6.9)
Shares issued under compensation program (in shares)		915
Shares and units tendered for tax withholding obligations	(9.6)					$ (9.6)
Shares and units tendered for tax withholding obligations (in shares)		(230)				230
Series A Preferred Stock dividends
Preferred stock dividends	(45.8)			(45.8)
Dividends in excess of retained earnings			(45.8)	45.8
Deemed dividends - accretion of beneficial conversion feature	(16.0)		(16.0)					16.0
Common stock dividends
Common stock dividends	(423.0)			(423.0)
Dividends in excess of retained earnings			(423.0)	423.0
Distributions to noncontrolling interests	(91.1)						(91.1)
Contributions from noncontrolling interests	403.5						403.5
Sale of ownership interests in subsidiaries, net	1,611.6		(8.1)				1,619.7
Other comprehensive income (loss)	(11.3)				(11.3)
Net income (loss)	24.2			(49.1)			73.3
Balance at Jun. 30, 2019	8,939.1	$ 0.2	5,687.8	(179.5)	83.0	$ (49.2)	3,396.8
Balance (in shares) at Jun. 30, 2019		232,476				896
Series A Preferred Stock at Jun. 30, 2019								261.7
Balance at Mar. 31, 2019	7,337.3	$ 0.2	5,925.7	(169.3)	48.9	$ (49.2)	1,581.0
Balance (in shares) at Mar. 31, 2019		232,475				895
Series A Preferred Stock at Mar. 31, 2019								253.6
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Compensation on equity grants	16.2		16.2
Distribution equivalent rights	(3.3)		(3.3)
Shares issued under compensation program (in shares)		2
Shares and units tendered for tax withholding obligations (in shares)		(1)				1
Series A Preferred Stock dividends
Preferred stock dividends	(22.9)			(22.9)
Dividends in excess of retained earnings			(22.9)	22.9
Deemed dividends - accretion of beneficial conversion feature	(8.1)		(8.1)					8.1
Common stock dividends
Common stock dividends	(211.7)			(211.7)
Dividends in excess of retained earnings			(211.7)	211.7
Distributions to noncontrolling interests	(69.7)						(69.7)
Contributions from noncontrolling interests	206.7						206.7
Sale of ownership interests in subsidiaries, net	1,611.6		(8.1)				1,619.7
Other comprehensive income (loss)	34.1				34.1
Net income (loss)	48.9			(10.2)			59.1
Balance at Jun. 30, 2019	8,939.1	$ 0.2	5,687.8	(179.5)	83.0	$ (49.2)	3,396.8
Balance (in shares) at Jun. 30, 2019		232,476				896
Series A Preferred Stock at Jun. 30, 2019								261.7
Balance at Dec. 31, 2019	8,442.9	$ 0.2	5,221.2	(339.6)	92.5	$ (53.5)	3,522.1
Balance (in shares) at Dec. 31, 2019		232,844				1,010
Series A Preferred Stock at Dec. 31, 2019								278.8
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Compensation on equity grants	33.1		33.1
Distribution equivalent rights	(5.6)		(5.6)
Shares issued under compensation program (in shares)		439
Shares and units tendered for tax withholding obligations	(3.4)					$ (3.4)
Shares and units tendered for tax withholding obligations (in shares)		(106)				106
Series A Preferred Stock dividends
Preferred stock dividends	(45.8)			(45.8)
Dividends in excess of retained earnings			(45.8)	45.8
Deemed dividends - accretion of beneficial conversion feature	(18.2)		(18.2)					18.2
Common stock dividends
Common stock dividends	(235.6)			(235.6)
Dividends in excess of retained earnings			(235.6)	235.6
Distributions to noncontrolling interests	(209.9)						(209.9)
Contributions from noncontrolling interests	25.7						25.7
Other comprehensive income (loss)	(70.9)				(70.9)
Net income (loss)	(1,643.2)			(1,656.8)			13.6
Balance at Jun. 30, 2020	6,269.1	$ 0.2	4,949.1	(1,996.4)	21.6	$ (56.9)	3,351.5
Balance (in shares) at Jun. 30, 2020		233,177				1,116
Series A Preferred Stock at Jun. 30, 2020								297.0
Balance at Mar. 31, 2020	6,372.5	$ 0.2	4,991.7	(2,077.4)	168.4	$ (56.6)	3,346.2
Balance (in shares) at Mar. 31, 2020		233,110				1,092
Series A Preferred Stock at Mar. 31, 2020								287.8
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Compensation on equity grants	16.1		16.1
Distribution equivalent rights	(3.3)		(3.3)
Shares issued under compensation program (in shares)		91
Shares and units tendered for tax withholding obligations	(0.3)					$ (0.3)
Shares and units tendered for tax withholding obligations (in shares)		(24)				24
Series A Preferred Stock dividends
Preferred stock dividends	(22.9)			(22.9)
Dividends in excess of retained earnings			(22.9)	22.9
Deemed dividends - accretion of beneficial conversion feature	(9.2)		(9.2)					9.2
Common stock dividends
Common stock dividends	(23.3)			(23.3)
Dividends in excess of retained earnings			(23.3)	23.3
Distributions to noncontrolling interests	(105.9)						(105.9)
Contributions from noncontrolling interests	15.1						15.1
Other comprehensive income (loss)	(146.8)				(146.8)
Net income (loss)	177.1			81.0			96.1
Balance at Jun. 30, 2020	$ 6,269.1	$ 0.2	$ 4,949.1	$ (1,996.4)	$ 21.6	$ (56.9)	$ 3,351.5
Balance (in shares) at Jun. 30, 2020		233,177				1,116
Series A Preferred Stock at Jun. 30, 2020								$ 297.0