Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	AOCI Attributable to Parent [Member]	Total
Balances (in shares) at Dec. 31, 2015	5,346
Balances at Dec. 31, 2015	$ 5	$ 275,636	$ (179,733)	$ (1,777)	$ 94,131
Issuance of common stock from exercise of vested stock options, vesting of restricted stock units and vesting of options and shares subject to repurchase (Note 10) (in shares)	87				38
Issuance of common stock from exercise of vested stock options, vesting of restricted stock units and vesting of options and shares subject to repurchase (Note 10)	$ 1	569			$ 570
Tax withholding related to vesting of restricted stock units		(362)			(362)
Issuance of common stock under employee stock purchase plan (in shares)	42
Issuance of common stock under employee stock purchase plan		548			548
Issuance of unrestricted common stock in connection with acquisition of SocialMoov S.A.S. (in shares)	66
Issuance of unrestricted common stock in connection with acquisition of SocialMoov S.A.S.
Stock-based compensation expense		10,295			10,295
Net loss			(16,480)		(16,480)
Foreign currency translation adjustments and other, net		6		(1,110)	(1,104)
Balances (in shares) at Dec. 31, 2016	5,541
Balances at Dec. 31, 2016	$ 6	286,692	(196,213)	(2,887)	87,598
Issuance of common stock from exercise of vested stock options, vesting of restricted stock units and vesting of options and shares subject to repurchase (Note 10) (in shares)	79
Issuance of common stock from exercise of vested stock options, vesting of restricted stock units and vesting of options and shares subject to repurchase (Note 10)		11			11
Tax withholding related to vesting of restricted stock units		(604)			$ (604)
Issuance of common stock under employee stock purchase plan (in shares)	43				43
Issuance of common stock under employee stock purchase plan		362			$ 362
Issuance of unrestricted common stock in connection with acquisition of SocialMoov S.A.S. (in shares)	66
Issuance of unrestricted common stock in connection with acquisition of SocialMoov S.A.S.
Stock-based compensation expense		4,704			4,704
Net loss			(31,491)		(31,491)
Foreign currency translation adjustments and other, net		(2)		2,205	2,203
Balances (in shares) at Dec. 31, 2017	5,729
Balances at Dec. 31, 2017	$ 6	291,163	(227,704)	(682)	62,783
Tax withholding related to vesting of restricted stock units		(327)			$ (327)
Issuance of common stock under employee stock purchase plan (in shares)	86				86
Issuance of common stock under employee stock purchase plan		305			$ 305
Stock-based compensation expense		3,971			3,971
Net loss			(41,244)		(41,244)
Foreign currency translation adjustments and other, net		4		(356)	(352)
Issuance of common stock from vesting of restricted stock units (Note 10) (in shares)	123
Issuance of common stock from vesting of restricted stock units (Note 10)
Balances (in shares) at Dec. 31, 2018	5,938
Balances at Dec. 31, 2018	$ 6	295,116	(264,713)	(1,038)	29,371
Impact of adoption of ASC 606 on January 1, 2018 (Note 3)			$ 4,235		$ 4,235