Annual report pursuant to Section 13 and 15(d)

Property, Equipment and Software - Additional Information (Detail)

v3.8.0.1
Property, Equipment and Software - Additional Information (Detail) - USD ($)
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Property, Plant and Equipment [Line Items]      
Depreciation and amortization expense for property, equipment and software $ 27,200,000 $ 24,500,000 $ 20,600,000
Carrying amount of capitalized development costs 73,400,000 55,400,000  
Accumulated amortization (27,800,000) (19,800,000)  
Capitalization of software development costs 18,000,000 13,700,000 10,500,000
Loss on disposal of software in development (524,000) (497,000) (3,070,000)
Capitalized Computer Software, Impairments 0 0  
Impairment of Leasehold 0 0  
Disposal of fixed assets 500,000 600,000 1,300,000
Loss on disposal of fixed assets 500,000 600,000 (200,000)
Software      
Property, Plant and Equipment [Line Items]      
Depreciation and amortization expense for property, equipment and software $ 8,000,000 $ 5,800,000 3,300,000
Weighted-average useful life (in years) 4 years 9 months 18 days    
Leasehold Improvements      
Property, Plant and Equipment [Line Items]      
Weighted-average useful life (in years) 12 years    
Product Development | Software      
Property, Plant and Equipment [Line Items]      
Loss on disposal of software in development     1,400,000
General and Administrative | Leasehold Improvements      
Property, Plant and Equipment [Line Items]      
Tangible asset impairment charges     $ 1,500,000