Annual report pursuant to Section 13 and 15(d)

Commitments and Contingencies - Additional Information (Detail)

v2.4.1.9
Commitments and Contingencies - Additional Information (Detail) (USD $)
In Millions, unless otherwise specified
 3 Months Ended 12 Months Ended
Dec. 31, 2012
Dec. 31, 2014
Dec. 31, 2013
Sep. 30, 2012
Operating Leased Assets [Line Items]        
Rent expense $ 0.1us-gaap_LeaseAndRentalExpense $ 0.5us-gaap_LeaseAndRentalExpense $ 0.3us-gaap_LeaseAndRentalExpense $ 0.3us-gaap_LeaseAndRentalExpense
Lease One [Member]        
Operating Leased Assets [Line Items]        
Lease commenced date   2011-07    
Lease amended date   2013-10    
Lease Two [Member]        
Operating Leased Assets [Line Items]        
Lease commenced date   2012-03    
Lease amendment commenced date   2014-03    
Lease Three [Member]        
Operating Leased Assets [Line Items]        
Lease commenced date   2014-08    
Operating lease term, years   5 years