Earnings per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended									9 Months Ended	12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Apr. 01, 2017	Dec. 31, 2017	Dec. 31, 2019	Dec. 31, 2018	Jan. 31, 2018
EPS numerator:
(Loss) income from continuing operations, net of income taxes	$ (290.2)	$ (74.3)	$ 42.9	$ 133.3	$ 233.5	$ 83.9	$ 120.0	$ 208.3	$ (195.5)	$ 713.1	$ (188.3)	$ 645.7
Less: Series A Convertible Preferred Stock dividends									0.0	179.5	0.0	102.5
Less: Net income attributable to noncontrolling interests									4.8	15.2	26.2	16.9
(Loss) income from continuing operations attributable to common stockholders, before allocation of earnings to participating securities									(200.3)	518.4	(214.5)	526.3
Less: Earnings allocated to participating securities									0.0	129.0	0.0	7.9
(Loss) income from continuing operations attributable to common stockholders, after allocation of earnings to participating securities (1)									(200.3)	389.4	(214.5)	518.4
Income (loss) from discontinued operations, net of income taxes									(16.2)	(19.8)	3.2	18.1
Less: Income (loss) from discontinued operations allocated to participating securities									0.0	(4.9)	0.0	0.3
Income (loss) from discontinued operations attributable to common stockholders, after allocation of earnings to participating securities									(16.2)	(14.9)	3.2	17.8
Net (loss) income attributable to common stockholders, after allocation of earnings to participating securities (1)									$ (216.5)	$ 374.5	$ (211.3)	$ 536.2
EPS denominator:
Weighted average shares outstanding — basic	97.3	102.2	107.0	108.5	113.1	118.6	124.5	120.9	18.3	101.1	103.7	119.3
Impact of dilutive securities									0.0	1.4	0.0	1.7
Weighted average shares outstanding — diluted (2)									18.3	102.5	103.7	121.0
Basic EPS attributable to common stockholders:
Basic (loss) income per share	$ (3.12)	$ (0.77)	$ 0.38	$ 1.18	$ 1.99	$ 0.64	$ 0.94	$ 0.84	$ (10.93)	$ 3.85	$ (2.07)	$ 4.35
Income (loss) from discontinued operations									(0.88)	(0.15)	0.03	0.15
Net (loss) income attributable to common stockholders									(11.81)	3.70	(2.04)	4.50
Diluted EPS attributable to common stockholders:
Diluted (loss) income per share	$ (3.12)	$ (0.77)	$ 0.37	$ 1.15	$ 1.97	$ 0.63	$ 0.93	$ 0.83	(10.93)	3.81	(2.07)	4.28
Income (loss) from discontinued operations									(0.88)	(0.14)	0.03	0.15
Net (loss) income attributable to common stockholders									$ (11.81)	$ 3.67	$ (2.04)	$ 4.43
Undistributed Earnings (Loss) Allocated to Participating Securities, Diluted										$ 1.2		$ 0.1
Weighted average shares outstanding — diluted	97.3	102.2	108.1	110.5	114.7	120.3	126.0	123.2		33.5		2.1
Earnings per Share (EPS) (Textuals) [Abstract]
Antidilutive shares excluded from EPS calculation									0.3		1.9	0.1
Effect of Plan
Earnings per Share (EPS) (Textuals) [Abstract]
Convertible preferred stock, shares issued upon conversion									46.2
Convertible Preferred Stock
Earnings per Share (EPS) (Textuals) [Abstract]
Preferred Stock, shares issued (in shares)	0.0				30.0						0.0	30.0	30.0
Common Stock | Common Stock
Earnings per Share (EPS) (Textuals) [Abstract]
Convertible preferred stock, shares issued upon conversion													59.3