Annual report pursuant to Section 13 and 15(d)

Long-Term Debt - Schedule of Long-Term Debt (Detail)

v3.8.0.1
Long-Term Debt - Schedule of Long-Term Debt (Detail) - USD ($)
$ in Millions
Dec. 31, 2017
Dec. 31, 2016
Debt Instrument [Line Items]    
Convertible senior notes, carrying value of liability component $ 1,070.0 $ 1,024.8
Other 7.9 13.1
Total 2,268.1 1,447.9
Less: current portion 102.4 9.5
Long-term portion 2,165.7 1,438.4
Prior Senior Secured Credit Facility [Member]    
Debt Instrument [Line Items]    
Borrowings under senior secured credit facility, carrying value   $ 410.0
New Senior Secured Credit Facility [Member]    
Debt Instrument [Line Items]    
Borrowings under senior secured credit facility, carrying value $ 1,190.2