Annual report pursuant to Section 13 and 15(d)

Intangible Assets - Additional Information (Detail)

v3.8.0.1
Intangible Assets - Additional Information (Detail) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Finite-Lived Intangible Assets [Line Items]      
Accumulated amortization $ 9,700 $ 16,100  
Intangible assets, net 28,372 43,809  
Gross intangible assets 38,100 59,900  
Amortization of intangible assets 5,500 $ 5,200 $ 4,000
Estimated future amortization expense of intangible assets, 2018 3,400    
Estimated future amortization expense of intangible assets, 2019 2,800    
Estimated future amortization expense of intangible assets, 2020 2,600    
Estimated future amortization expense of intangible assets, 2021 2,500    
Estimated future amortization expense of intangible assets, 2022 2,500    
Estimated future amortization expense of intangible assets, thereafter 14,600    
Impairment Test on Intangible Assets      
Finite-Lived Intangible Assets [Line Items]      
Accumulated amortization 8,400    
Intangible assets, net 10,500    
Gross intangible assets $ 18,900