Annual report pursuant to Section 13 and 15(d)

Long-term Debt - Summary of Components of Convertible Notes (Detail)

v3.8.0.1
Long-term Debt - Summary of Components of Convertible Notes (Detail) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Aug. 31, 2017
Debt Instrument [Line Items]        
Interest expense $ 65,472 $ 45,241 $ 26,385  
4.125% Convertible Senior Notes Due September 1, 2022 [Member]        
Debt Instrument [Line Items]        
Principal 150,000     $ 150,000
Accrued interest 3,000      
Unamortized financing costs (5,000)      
Carrying value of convertible notes 148,000     $ 145,000
Interest expense $ 3,000