Summary of Significant Accounting Policies - Property, Equipment and Software (Details)
12 Months Ended
Dec. 31, 2015
Computer and other equipment  
Property, Plant and Equipment [Line Items]  
Useful lives 3 years
Leasehold improvements  
Property, Plant and Equipment [Line Items]  
Estimated useful lives Shorter of 10 years or lease term
Leasehold improvements | Maximum  
Property, Plant and Equipment [Line Items]  
Useful lives 10 years
Office furniture  
Property, Plant and Equipment [Line Items]  
Useful lives 5 years
Software | Minimum  
Property, Plant and Equipment [Line Items]  
Useful lives 3 years
Software | Maximum  
Property, Plant and Equipment [Line Items]  
Useful lives 5 years