Financial Instruments and Fair Value Measurements - Additional Information (Detail) - USD ($)
3 Months Ended 9 Months Ended 12 Months Ended
Jun. 30, 2016
Dec. 31, 2015
Sep. 30, 2016
Dec. 31, 2015
Dec. 31, 2014
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]          
Transfers between level 1 and level 2, assets     $ 0    
Transfers between level 2 and level 1, assets     0    
Transfer of liabilities into level 3     0    
Transfer of liabilities out of level 3     0    
Impairment of intangible asset $ 104,500,000 $ 89,600,000 104,517,000    
Intangible assets   101,500,000   $ 101,500,000  
Convertible Senior Unsecured Notes          
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]          
Convertible senior notes     287,500,000    
Convertible Senior Unsecured Notes | Fair Value, Inputs, Level 2          
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]          
Convertible senior notes, fair value     273,800,000    
In Process Research and Development          
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]          
Impairment of intangible asset $ 104,500,000   104,517,000 89,557,000  
Intangible assets   $ 101,500,000 $ 0 $ 101,500,000 $ 212,900,000