Stockholders' Equity - Additional Information (Detail) - USD ($)					3 Months Ended		55 Months Ended
	Dec. 20, 2017	Feb. 08, 2017	May 12, 2016	Aug. 13, 2014	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Jun. 06, 2011
Stockholders Equity [Line Items]
Preferred stock, shares authorized					10,000,000
Preferred stock, par value					$ 0.001
Preferred stock, outstanding								0	0
Common stock reserved for future issuance					9,180,563
Unrecognized compensation expense					$ 400,000
Unrecognized stock-based compensation expense, weighted average period of recognition					1 year 4 months 24 days
Accumulated Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Net of Tax					$ 2,800,000			$ 2,700,000
Restricted Stock Units (RSUs)
Stockholders Equity [Line Items]
Unrecognized compensation expense					$ 4,600,000
Unrecognized stock-based compensation expense, weighted average period of recognition					2 years 10 months 24 days
Repurchase of common stock (in shares)					42,447	16,160
2010 Bonus and Incentive Plan
Stockholders Equity [Line Items]
Common stock reserved for future issuance					0
2011 Plan
Stockholders Equity [Line Items]
Common stock reserved for future issuance										400,000
Number of shares available for grant										859,956
Increase in shares of common stock authorized for issuance			2,000,000				1,000,000
2011 Plan | Restricted Stock Units (RSUs)
Stockholders Equity [Line Items]
Aggregate restricted stock units outstanding					1,542,490
2007 Plan and 2010 Plan
Stockholders Equity [Line Items]
Number of shares available for grant										459,956
Loan and Security Agreements | East West Bank | Revolving Credit Facility
Stockholders Equity [Line Items]
Borrowing capacity under credit facility		$ 16,000,000
Loan and Security Agreements | Venture Lending & Leasing VII and VIII, Inc. | Term Loan Facility
Stockholders Equity [Line Items]
Borrowing capacity under credit facility		$ 10,000,000
2014 Consultant Warrant
Stockholders Equity [Line Items]
Warrant exercise price				$ 10.70	$ 10.70
Warrants expiration date				Aug. 13, 2019	Aug. 13, 2019
Warrants exercised					0
VLL7 Warrant
Stockholders Equity [Line Items]
Warrants issued to purchase common stock		290,000
Warrant exercise price		$ 2.00
Warrants expiration date		Feb. 08, 2022
Private placement warrant estimated volatility		78.80%
Private placement warrant risk free interest rate		1.94%
Private placement warrant dividend yield		0.00%
Private placement warrant expected life (in years)		5 years
Common stock warrants fair value		$ 1,037,500
Warrants expiration period		5 years
EWB Warrant
Stockholders Equity [Line Items]
Warrants issued to purchase common stock		40,000
Warrant exercise price		$ 3.64			$ 3.64
Warrants expiration date		Feb. 08, 2022			Feb. 08, 2022
Private placement warrant estimated volatility		78.80%
Private placement warrant risk free interest rate		1.94%
Private placement warrant dividend yield		0.00%
Private placement warrant expected life (in years)		5 years
Common stock warrants fair value		$ 125,000
Warrants expiration period		5 years
VLL8 Warrant
Stockholders Equity [Line Items]
Warrants issued to purchase common stock		290,000
Warrant exercise price		$ 2.00
Warrants expiration date		Feb. 08, 2022
Private placement warrant estimated volatility		78.80%
Private placement warrant risk free interest rate		1.94%
Private placement warrant dividend yield		0.00%
Private placement warrant expected life (in years)		5 years
Common stock warrants fair value		$ 1,037,500
Warrants expiration period		5 years
Previous Lender
Stockholders Equity [Line Items]
Warrants to purchase common stock cancelled		400,000
2017 Consultant Warrant
Stockholders Equity [Line Items]
Warrants issued to purchase common stock		60,000
Warrant exercise price		$ 4.60			$ 4.60
Warrants expiration date		Feb. 08, 2019			Feb. 08, 2019
Private placement warrant estimated volatility		78.80%
Private placement warrant risk free interest rate		1.22%
Private placement warrant dividend yield		0.00%
Private placement warrant expected life (in years)		2 years
Common stock warrants fair value		$ 119,000
Warrants expiration period		2 years
Maximum | Common Stock
Stockholders Equity [Line Items]
Shares issued, price per share					$ 4.00
Maximum | Common Stock | 2014 Consultant Warrant
Stockholders Equity [Line Items]
Warrants issued to purchase common stock				85,000
Series A Participating Preferred Stock
Stockholders Equity [Line Items]
Preferred stock, shares authorized					40,000
Preferred stock, par value					$ 0.001
Preferred stock, outstanding								0	0
Series B Preferred Stock
Stockholders Equity [Line Items]
Preferred stock, shares authorized					5,000,000
Preferred stock, par value	$ 0.001				$ 0.001
Preferred stock, outstanding					3,000,000
Shares issued, price per share	$ 4.00
Total purchase price payable	$ 20,000,000
Convertible preferred stock, terms of conversion					Each Share shall be convertible into the Company’s common stock (i) following the sixth (6th) anniversary of the initial closing of the Private Placement or (ii) if earlier, during the thirty (30) day period following the last trading day of any period of three (3) or more consecutive trading days that the closing market price of the Company’s common stock exceeds $10.00. Each Share is convertible at the option of the holder of shares of Series B Preferred Stock into such number of shares of the Company’s common stock
Convertible preferred stock, threshold closing market price of entity stock	$ 10.00
Percentage of beneficially ownership limitation in excess of outstanding common stock immediately after effect to applicable conversion	19.90%
Minimum conversion price					$ 3.27
Dividend payment terms					Each Share is entitled to an annual dividend of 5% for the first six (6) years following the issuance of such Share and 3% for each year thereafter, with the Company retaining the option to settle each year’s dividend after the tenth (10th) year in cash. The dividends accrue and are payable in kind upon such time as the Shares convert into the Company’s common stock
Annual dividend for first six years					5.00%
Annual dividend for each year after sixth year					3.00%
Expected price per share distributable to stockholders	$ 4.00
Series B Preferred Stock | Common Stock
Stockholders Equity [Line Items]
Preferred stock shares convertible into common stock					3,000,000
Series B Preferred Stock | Private Placement at Initial Closing of Transaction
Stockholders Equity [Line Items]
Issuance of stock (in shares)	3,000,000
Shares issued, price per share	$ 4.00
Total purchase price payable	$ 12,000,000
Series B Preferred Stock | Private Placement at Second Closing of Transaction
Stockholders Equity [Line Items]
Issuance of stock (in shares)	2,000,000
Shares issued, price per share	$ 4.00
Total purchase price payable	$ 8,000,000
Series B Preferred Stock | Maximum
Stockholders Equity [Line Items]
Preferred stock, shares authorized					5,000,000
Preferred stock, issued	5,000,000