Long-Term Debt - Extinguishment of Debt (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended
	Jul. 31, 2017	Sep. 30, 2017
Line of Credit Facility [Line Items]
Debt extinguishment costs		$ 5.3
Senior Secured Credit Facility | Line of Credit
Line of Credit Facility [Line Items]
Early payment transaction fee on retirement of Term Loan Facility	$ 51.6
2.125% Cash Convertible Senior Notes Due 2019
Line of Credit Facility [Line Items]
Early payment transaction fee on retirement of Term Loan Facility	34.4
Write-off of debt discount and issuance costs on retirement	35.0
Convertible Notes Hedges
Line of Credit Facility [Line Items]
Settlement of derivative, amounts received (paid)	0.6
Convertible Notes Warrants
Line of Credit Facility [Line Items]
Settlement of derivative, amounts received (paid)	(0.5)
Repayment of Cash Convertible Notes at discount to par value	$ 2.2