Summary of Intangible Assets (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Total intangible assets, Gross Carrying Amount	$ 6,161	$ 6,161
Total intangible assets, Accumulated Amortization	3,183	4,419
Total intangible assets, Net	$ 2,978	1,742
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Total intangible assets, Weighted Average Amortization Period (Years)	4 years 6 months
Total intangible assets, Gross Carrying Amount	$ 272	272
Total intangible assets, Accumulated Amortization	151	211
Total intangible assets, Net	$ 121	61
Customer backlog
Finite-Lived Intangible Assets [Line Items]
Total intangible assets, Weighted Average Amortization Period (Years)	1 year 6 months
Total intangible assets, Gross Carrying Amount	$ 93	93
Total intangible assets, Accumulated Amortization	$ 93	93
Core technologies
Finite-Lived Intangible Assets [Line Items]
Total intangible assets, Weighted Average Amortization Period (Years)	5 years 1 month 6 days
Total intangible assets, Gross Carrying Amount	$ 5,796	5,796
Total intangible assets, Accumulated Amortization	2,939	4,115
Total intangible assets, Net	$ 2,857	$ 1,681