Goodwill and Intangible Assets - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Acquired Finite-Lived Intangible Assets [Line Items]
Impairment of long-lived assets	$ 0
Estimated useful life of the acquired intangible assets	6 years 7 months 6 days
Amortization expense	$ 300,000	$ 400,000	$ 400,000
Trade Names [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Estimated useful life of the acquired intangible assets	3 years
Developed Technology [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Estimated useful life of the acquired intangible assets	7 years
Customer Relationships [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Estimated useful life of the acquired intangible assets	7 years