Basis of Presentation (Details) - USD ($) $ in Millions		3 Months Ended			6 Months Ended	9 Months Ended
		Sep. 30, 2018	Sep. 30, 2017	Apr. 01, 2017	Sep. 30, 2017	Sep. 30, 2018	Apr. 03, 2017
Successor
Fresh-Start Adjustment [Line Items]
Gain on settlement of claims	[1]					$ (12.8)
Fresh start adjustments, net	[1]					0.0
Fresh start income tax adjustments, net	[1]					0.0
Professional fees	[2]					0.0
Accounts payable settlement gains						0.0
Interest income						0.0
Reorganization items, net		$ 0.0	$ 0.0		$ 0.0	12.8
Cash paid for Reorganization items, net						$ 0.0
Predecessor
Fresh-Start Adjustment [Line Items]
Gain on settlement of claims	[1]			$ (3,031.2)
Fresh start adjustments, net	[1]			3,363.1
Fresh start income tax adjustments, net	[1]			253.9
Professional fees	[2]			42.5
Accounts payable settlement gains				(0.7)
Interest income				(0.4)
Reorganization items, net				(627.2)
Cash paid for Reorganization items, net				$ 45.8
Voting shares received upon reorganization (less than 50%)							50.00%

[1] Refer to Note 2. “Emergence from the Chapter 11 Cases and Fresh Start Reporting” in the Company's Annual Report on Form 10-K for the year ended December 31, 2017 for further information related to the adjustments recorded in the period January 1 through April 1, 2017.

[2] Professional fees are only those that were directly related to the reorganization including, but not limited to, fees associated with advisors to the Debtors, the unsecured creditors' committee and certain other secured and unsecured creditors.