Long-Term and Other Debt - (Loss) Gain on Debt Financing Transactions (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Debt Disclosure [Abstract]
Repurchase and cancellation of principal balance at discount	$ 0.0	$ 26.0	$ 0.0
Unamortized debt discount and deferred financing costs	(26.4)	(0.8)	0.0
Third party debt issuance fees	(11.7)	0.0	0.0
(Loss) gain on debt financing transactions	$ (38.1)	$ 25.2	$ 0.0