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Capitalized Software Development Costs - Summary of Capitalized Software Development Costs (Detail) - USD ($)
$ in Thousands
9 Months Ended 12 Months Ended
Sep. 30, 2017
Dec. 31, 2016
Capitalized Computer Software Net [Line Items]    
Gross carrying amount $ 35,278 $ 30,658
Accumulated amortization (25,606) (21,866)
Net carrying amount 9,672 8,792
Capitalized software development costs [Member]    
Capitalized Computer Software Net [Line Items]    
Gross carrying amount $ 35,278 $ 30,658
Amortization period 3 years 3 years
Accumulated amortization $ (25,606) $ (21,866)
Net carrying amount $ 9,672 $ 8,792