Preferred Stock, Common Stock and Stockholders' Equity - Stock Options - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	May 31, 2007	Aug. 31, 2013	Jan. 01, 2015
Stock-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for issuance	1,043,457	769,250
Number of stock options granted	64,000
Intrinsic value, common stock price	$ 5.90	$ 7.45
Common stock price on the date of exercise of stock option	$ 0.29
Issuance of common stock upon exercise of stock option, Shares	5,250
Stock options vested	173,791
Total intrinsic value of stock options exercised	$ 33,810	$ 0
Weighted Average Grant Date Fair Value Per Share, Granted	$ 4.76	$ 6.33
Common stock options [Member]
Stock-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock price on the date of exercise of stock option	$ 6.73
Options Granted [Member]
Stock-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options granted, weighted average term	10 years
Number of stock options granted	64,000	501,500
Options Granted [Member] | Minimum [Member]
Stock-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options granted, vesting period	1 year
Options Granted [Member] | Maximum [Member]
Stock-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options granted, vesting period	4 years
2007 Equity Incentive Plan [Member]
Stock-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for issuance	0		450,000
Issuance of common stock upon exercise of stock option, Shares	332,000
Stock options vested	287,000	230,500
Number of options exercised	1	0
2013 Equity Incentive Award Plan [Member]
Stock-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for issuance				510,000
Additional common stock reserved for issuance	243,870
Shares of common stock available for issuance description	In addition, the number of shares of common stock available for issuance under the 2013 Plan will be annually increased on the first day of each fiscal year during the term of the 2013 Plan, beginning with the 2014 fiscal year, by an amount equal to the least of: (i) 300,000 shares; (ii) four percent of the outstanding shares of common stock as of the last day of the immediately preceding fiscal year; or (iii) such other amount as the Company’s board of directors may determine.
Options available for future grant	188,370
2013 Equity Incentive Award Plan [Member] | Subsequent Event [Member]
Stock-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for issuance					244,484
Options available for future grant					432,854
2013 Equity Incentive Award Plan [Member] | Annual Increase in Shares [Member]
Stock-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for issuance	300,000
Reserve percentage for issuance of shares	4.00%