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, 2016	$ 5,724.4	$ 0.2	$ 5,506.2	$ (187.3)	$ (38.3)	$ (32.2)	$ 475.8
Balance (in shares) at Dec. 31, 2016		184,721				514
Series A Preferred Stock at Dec. 31, 2016								$ 190.8
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Impact of accounting standard adoption (see Note 3)	56.1			56.1
Compensation on equity grants	31.7		31.7
Distribution equivalent rights	(7.0)		(7.0)
Shares issued under compensation program (in shares)		258
Shares and units tendered for tax withholding obligations	(3.1)					$ (3.1)
Shares and units tendered for tax withholding obligations (in shares)		(67)				67
Issuance of common stock	1,558.4		1,558.4
Issuance of common stock (in shares)		30,721
Series A Preferred Stock dividends
Dividends	(68.8)			(68.8)
Dividends in excess of retained earnings			(68.8)	68.8
Deemed dividends - accretion of beneficial conversion feature	(19.0)		(19.0)					19.0
Common stock dividends
Dividends	(553.2)			(553.2)
Dividends in excess of retained earnings			(553.2)	553.2
Distributions to noncontrolling interests	(41.8)						(41.8)
Contributions from noncontrolling interests	93.8						93.8
Purchase of noncontrolling interests in subsidiary, net of tax impact	(25.9)		(13.4)				(12.5)
Other comprehensive income (loss)	(5.2)				(5.2)
Net income (loss)	(195.0)			(229.3)			34.3
Balance at Sep. 30, 2017	6,545.4	$ 0.2	6,434.9	(360.5)	(43.5)	$ (35.3)	549.6
Balance (in shares) at Sep. 30, 2017		215,633				581
Series A Preferred Stock at Sep. 30, 2017								209.8
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 (see Note 3)	5.2			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 - share settled		59
Series A Preferred Stock dividends
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
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 (see Note 17)	1.1						1.1
Purchase of noncontrolling interests in subsidiary, net of tax impact	(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