Earnings per Share (EPS) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions			1 Months Ended	3 Months Ended			6 Months Ended	9 Months Ended
		Aug. 23, 2017	Sep. 30, 2017	Sep. 30, 2017	Apr. 01, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Earnings Per Share [Line Items]
Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Diluted Share					$ (0.88)
Undistributed Earnings (Loss) Allocated to Participating Securities, Diluted				$ 0.6			$ 0.4
Basic EPS attributable to common stockholders:
Weighted Average Number of Shares Outstanding, Diluted				34.2			36.7
Successor
Earnings Per Share [Line Items]
Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Diluted Share				$ (0.02)			$ (0.05)
Participating Securities, Distributed and Undistributed Earnings (Loss), Basic				$ 51.6			$ 50.6
Antidilutive shares excluded from EPS calculation (less than 0.1 million for the period April 2 through June 30, 2017)				0.1			0.1
Weighted Average Number Diluted Shares Outstanding Adjustment				1.5			1.0
EPS numerator:
Income (loss) from continuing operations, net of income taxes				$ 233.7			$ 335.1
Less: Series A Convertible Preferred Stock dividends				23.5			138.6
Less: Net income attributable to noncontrolling interests				5.1			8.9
Participating Securities, Distributed and Undistributed Earnings (Loss), Basic				51.6			50.6
Income (loss) from continuing operations attributable to common stockholders, after allocation of earnings to participating securities (1)	[1]			153.5			137.0
Loss from discontinued operations attributable to common stockholders, after allocation of earnings to participating securities				(3.7)			(6.4)
Loss from discontinued operations allocated to participating securities				(0.9)			(1.7)
Net Income (Loss) from Discontinued Operations Available to Common Shareholders, Basic				(2.8)			(4.7)
Income (Loss) from Continuing Operations Attributable to Common Stockholders, Before Allocation of Earnings to Participating Securities				$ 205.1			$ 187.6
Earnings Per Share, Diluted				$ 1.47			$ 1.32
Weighted average shares outstanding — basic				101.6			99.2
Net income (loss) attributable to common stockholders, after allocation of earnings to participating securities (1)	[1]			$ 150.7			$ 132.3
EPS denominator:
Weighted average shares outstanding — basic and diluted (in shares)	[2]			103.1			100.2
Basic EPS attributable to common stockholders:
Loss from continuing operations (in dollars per share)				$ 1.51			$ 1.38
Loss from discontinued operations (in dollars per share)				(0.03)			(0.05)
Net loss attributable to common stockholders (in dollars per share)				1.48			1.33
Diluted income (loss) per share (in dollars per share)				$ 1.49			$ 1.37
Income (Loss) from Continuing Operations Attributable to Common Stockholders, Before Allocation of Earnings to Participating Securities				$ 205.1			$ 187.6
Treasury Stock, Shares, Acquired		1.5	1.0				2.5
Predecessor
Earnings Per Share [Line Items]
Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Diluted Share						$ (2.09)		$ (2.43)
Participating Securities, Distributed and Undistributed Earnings (Loss), Basic					$ 0.0	$ 0.0		$ 0.0
Antidilutive shares excluded from EPS calculation (less than 0.1 million for the period April 2 through June 30, 2017)					0.2	0.4
Weighted Average Number Diluted Shares Outstanding Adjustment					0.0	0.0		0.0
EPS numerator:
Income (loss) from continuing operations, net of income taxes					$ (195.5)	$ (97.7)		$ (488.6)
Less: Series A Convertible Preferred Stock dividends					0.0	0.0		0.0
Less: Net income attributable to noncontrolling interests					4.8	1.8		3.5
Participating Securities, Distributed and Undistributed Earnings (Loss), Basic					0.0	0.0		0.0
Income (loss) from continuing operations attributable to common stockholders, after allocation of earnings to participating securities (1)	[1]				(200.3)	(99.5)		(492.1)
Loss from discontinued operations attributable to common stockholders, after allocation of earnings to participating securities					(16.2)	(38.1)		(44.5)
Loss from discontinued operations allocated to participating securities					0.0	0.0		0.0
Net Income (Loss) from Discontinued Operations Available to Common Shareholders, Basic					(16.2)	(38.1)		(44.5)
Income (Loss) from Continuing Operations Attributable to Common Stockholders, Before Allocation of Earnings to Participating Securities					$ (200.3)	$ (99.5)		$ (492.1)
Earnings Per Share, Diluted					$ (11.81)	$ (7.53)		$ (29.34)
Weighted average shares outstanding — basic					18.3	18.3		18.3
Net income (loss) attributable to common stockholders, after allocation of earnings to participating securities (1)	[1]				$ (216.5)	$ (137.6)		$ (536.6)
EPS denominator:
Weighted average shares outstanding — basic and diluted (in shares)	[2]				18.3	18.3		18.3
Basic EPS attributable to common stockholders:
Loss from continuing operations (in dollars per share)					$ (10.93)	$ (5.44)		$ (26.91)
Loss from discontinued operations (in dollars per share)					(0.88)	(2.09)		(2.43)
Net loss attributable to common stockholders (in dollars per share)					(11.81)	(7.53)		(29.34)
Diluted income (loss) per share (in dollars per share)					$ (10.93)	$ (5.44)		$ (26.91)
Income (Loss) from Continuing Operations Attributable to Common Stockholders, Before Allocation of Earnings to Participating Securities					$ (200.3)	$ (99.5)		$ (492.1)
Preferred Stock
Basic EPS attributable to common stockholders:
Conversion of stock, shares converted							14.2
Warrant
Basic EPS attributable to common stockholders:
Warrants unexercised, percent (less than 0.1%)			0.00%	0.00%			0.00%
Common Stock
Basic EPS attributable to common stockholders:
Conversion of stock, shares issued							34.2

[1] The reallocation adjustment for participating securities to arrive at the numerator to calculate diluted EPS was $0.6 million for the Successor three months ended September 30, 2017 and $0.4 million for the Successor period April 2 through September 30, 2017.

[2] The two-class method assumes that participating securities are not exercised or converted. As such, weighted average diluted shares outstanding excluded 34.2 million shares and 36.7 million shares related to the participating securities for the Successor three months ended September 30, 2017 and the Successor period April 2 through September 30, 2017, respectively.