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, 2017	$ 6,756.0	$ 0.2	$ 6,302.8	$ (77.2)	$ (29.9)	$ (35.6)	$ 595.7
Balance (in shares) at Dec. 31, 2017		217,567				586
Series A Preferred Stock at Dec. 31, 2017								$ 216.5
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Impact of accounting standard adoption				5.2	(5.2)
Compensation on equity grants	40.7		40.7
Distribution equivalent rights	(10.3)		(10.3)
Shares issued under compensation program (in shares)		361
Shares and units tendered for tax withholding obligations	(4.0)					$ (4.0)
Shares and units tendered for tax withholding obligations (in shares)		(80)				80
Issuance of common stock	572.0		572.0
Issuance of common stock (in shares)		11,376
Exercise of warrants - shares settled		59
Series A Preferred Stock dividends
Preferred stock dividends	(68.8)			(68.8)
Dividends in excess of retained earnings			(8.8)	8.8
Deemed dividends - accretion of beneficial conversion feature	(21.5)		(21.5)					21.5
Common stock dividends
Common stock dividends	(604.4)			(604.4)
Dividends in excess of retained earnings			(604.4)	604.4
Distributions to noncontrolling interests	(60.0)						(60.0)
Contributions from noncontrolling interests	611.7						611.7
Acquisition of related party	1.1						1.1
Purchase of noncontrolling interests in subsidiary	(0.1)						(0.1)
Other comprehensive income (loss)	(90.8)				(90.8)
Net income (loss)	148.6			108.2			40.4
Balance at Sep. 30, 2018	7,270.2	$ 0.2	6,270.5	(23.8)	(125.9)	$ (39.6)	1,188.8
Balance (in shares) at Sep. 30, 2018		229,283				666
Series A Preferred Stock at Sep. 30, 2018								238.0
Balance at Jun. 30, 2018	7,250.2	$ 0.2	6,233.7	60.0	(37.9)	$ (38.2)	1,032.4
Balance (in shares) at Jun. 30, 2018		225,487				640
Series A Preferred Stock at Jun. 30, 2018								230.6
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Compensation on equity grants	13.8		13.8
Distribution equivalent rights	(3.8)		(3.8)
Shares issued under compensation program (in shares)		126
Shares and units tendered for tax withholding obligations	(1.4)					$ (1.4)
Shares and units tendered for tax withholding obligations (in shares)		(26)				26
Issuance of common stock	202.5		202.5
Issuance of common stock (in shares)		3,696
Series A Preferred Stock dividends
Preferred stock dividends	(22.9)			(22.9)
Dividends in excess of retained earnings			37.1	(37.1)
Deemed dividends - accretion of beneficial conversion feature	(7.4)		(7.4)					7.4
Common stock dividends
Common stock dividends	(205.4)			(205.4)
Dividends in excess of retained earnings			(205.4)	205.4
Distributions to noncontrolling interests	(20.6)						(20.6)
Contributions from noncontrolling interests	164.4						164.4
Other comprehensive income (loss)	(88.0)				(88.0)
Net income (loss)	(11.2)			(23.8)			12.6
Balance at Sep. 30, 2018	7,270.2	$ 0.2	6,270.5	(23.8)	(125.9)	$ (39.6)	1,188.8
Balance (in shares) at Sep. 30, 2018		229,283				666
Series A Preferred Stock at Sep. 30, 2018								238.0
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	49.0		49.0
Distribution equivalent rights	(10.5)		(10.5)
Shares issued under compensation program (in shares)		1,327
Shares and units tendered for tax withholding obligations	(13.5)					$ (13.5)
Shares and units tendered for tax withholding obligations (in shares)		(335)				335
Series A Preferred Stock dividends
Preferred stock dividends	(68.8)			(68.8)
Dividends in excess of retained earnings			(68.8)	68.8
Deemed dividends - accretion of beneficial conversion feature	(24.4)		(24.4)					24.4
Common stock dividends
Common stock dividends	(634.8)			(634.8)
Dividends in excess of retained earnings			(634.8)	634.8
Distributions to noncontrolling interests	(181.1)						(181.1)
Contributions from noncontrolling interests	518.8						518.8
Sale of ownership interest in subsidiaries, net	1,611.5		(8.2)				1,619.7
Other comprehensive income (loss)	46.6				46.6
Net income (loss)	56.3			(96.4)			152.7
Balance at Sep. 30, 2019	8,819.9	$ 0.2	5,457.2	(226.8)	140.9	$ (53.1)	3,501.5
Balance (in shares) at Sep. 30, 2019		232,783				1,001
Series A Preferred Stock at Sep. 30, 2019								270.1
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
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Compensation on equity grants	16.1		16.1
Distribution equivalent rights	(3.7)		(3.7)
Shares issued under compensation program (in shares)		412
Shares and units tendered for tax withholding obligations	(3.9)					$ (3.9)
Shares and units tendered for tax withholding obligations (in shares)		(105)				105
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	(8.4)		(8.4)					8.4
Common stock dividends
Common stock dividends	(211.7)			(211.7)
Dividends in excess of retained earnings			(211.7)	211.7
Distributions to noncontrolling interests	(90.0)						(90.0)
Contributions from noncontrolling interests	115.3						115.3
Other comprehensive income (loss)	57.9				57.9
Net income (loss)	32.1			(47.3)			79.4
Balance at Sep. 30, 2019	$ 8,819.9	$ 0.2	$ 5,457.2	$ (226.8)	$ 140.9	$ (53.1)	$ 3,501.5
Balance (in shares) at Sep. 30, 2019		232,783				1,001
Series A Preferred Stock at Sep. 30, 2019								$ 270.1