Convertible of Senior Notes - Summary of Hedge Notes (Detail) (USD $)
In Thousands, except Share data, unless otherwise specified
3 Months Ended
Mar. 31, 2014
Mar. 31, 2015
Derivatives, Fair Value [Line Items]    
Note Hedges, Purchase $ 85,853  
Note Hedges [Member]    
Derivatives, Fair Value [Line Items]    
Note Hedges, Contract Date   2014-03
Note Hedges, Purchase   $ 85,853
Underlying Note Hedges, Shares   7,716,049