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	(5.2)
Compensation on equity grants	13.2		13.2
Distribution equivalent rights	(3.3)		(3.3)
Shares issued under compensation program (in shares)		51
Shares and units tendered for tax withholding obligations	(0.4)					$ (0.4)
Shares and units tendered for tax withholding obligations (in shares)		(8)				8
Issuance of common stock	57.7		57.7
Issuance of common stock (in shares)		1,163
Exercise of warrants - shares settled		59
Series A Preferred Stock dividends
Dividends - $23.75 per share	(22.9)			(22.9)
Dividends in excess of retained earnings			(22.9)	22.9
Deemed dividends - accretion of beneficial conversion feature	(7.0)		(7.0)					7.0
Common stock dividends
Dividends - $0.91 per share	(199.3)			(199.3)
Dividends in excess of retained earnings			(199.3)	199.3
Distributions to noncontrolling interests	(19.3)						(19.3)
Contributions from noncontrolling interests	280.1						280.1
Acquisition of related party	1.2						1.2
Other comprehensive income (loss)	69.5				69.5
Net income (loss)	38.9			22.9			16.0
Balance at Mar. 31, 2018	6,964.4	$ 0.2	6,141.2	(49.1)	34.4	$ (36.0)	873.7
Balance (in shares) at Mar. 31, 2018		218,832				594
Series A Preferred Stock at Mar. 31, 2018								223.5
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	16.5		16.5
Distribution equivalent rights	(3.6)		(3.6)
Shares issued under compensation program (in shares)		913
Shares and units tendered for tax withholding obligations	(9.6)					$ (9.6)
Shares and units tendered for tax withholding obligations (in shares)		(229)				229
Series A Preferred Stock dividends
Dividends - $23.75 per share	(22.9)			(22.9)
Dividends in excess of retained earnings			(22.9)	22.9
Deemed dividends - accretion of beneficial conversion feature	(7.9)		(7.9)					7.9
Common stock dividends
Dividends - $0.91 per share	(211.3)			(211.3)
Dividends in excess of retained earnings			(211.3)	211.3
Distributions to noncontrolling interests	(21.4)						(21.4)
Contributions from noncontrolling interests	196.8						196.8
Other comprehensive income (loss)	(45.4)				(45.4)
Net income (loss)	(24.7)			(38.9)			14.2
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