Business Combinations - Additional Information (Detail) - USD ($) shares in Thousands, $ in Thousands		12 Months Ended
	Feb. 12, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Business Acquisition [Line Items]
Purchase price attributable to goodwill		$ 16,768	$ 19,318
Number of RSUs, granted		405	446	169
SocialMoov [Member]
Business Acquisition [Line Items]
Acquisition date		Feb. 12, 2015
Business acquisition, purchase price	$ 13,288
Number of common stock, shares at the date of acquisition	91
Consideration in common stock	$ 4,337
Common stock value at the date of acquisition	8,858
Cash paid as contingent consideration			$ 93
Purchase price of net liabilities assumed	2,006	$ 3,627
Cash acquired from acquisition	1,120
Purchase price attributable to intangible assets	6,140
Purchase price attributable to goodwill	$ 8,034	$ 8,034
Additional shares of common stock issued in connection with acquisition	132
Common stock issued in connection with acquisition closing date fair value	$ 6,487
Additional shares of common stock issued in connection with acquisition, description		In addition, the Company agreed to issue 132 shares of common stock, valued at $6,487 upon the closing date of the acquisition using the Company’s closing date stock price immediately preceding the acquisition, to existing employee shareholders of SocialMoov in connection with the acquisition, which were conditioned upon such employees’ continuous employment with the Company. These shares were excluded from the purchase consideration and were recognized as post-acquisition stock-based compensation expense over the employees’ requisite service periods. The Company issued half of these shares in February 2016 and the remaining half in February 2017.
SocialMoov [Member] | RSUs [Member]
Business Acquisition [Line Items]
Number of RSUs, granted	31
Value of RSUs, granted	$ 959