Newly Adopted Accounting Standards and Accounting Standards Not Yet Implemented - Adjustments Due to ASC 606 (Details) - Successor - USD ($) $ in Millions		3 Months Ended
	Jan. 01, 2018	Mar. 31, 2018	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Investments and other assets		$ 343.6	$ 470.6
Adjustments due to ASU 2014-09		$ (22.5)
Investments and other assets
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Investments and other assets	$ 448.1		470.6
Adjustments due to ASU 2014-09	(22.5)
Retained earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Retained earnings	591.1		$ 613.6
Adjustments due to ASU 2014-09	$ (22.5)