Preferred Stock, Common Stock and Stockholders' Equity - Equity Incentive Award Plans - Additional Information (Detail) - USD ($)		1 Months Ended	12 Months Ended
	Apr. 27, 2016	Feb. 29, 2016	Dec. 31, 2016	Dec. 31, 2015	Jan. 01, 2017	Aug. 31, 2013	May 31, 2007
Stock-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for issuance			5,265,764	1,276,765
Options available for future grant			628,801	78,854
Number of stock options exchanged, outstanding			1,275,624	1,037,500
Unrecognized compensation costs			$ 1,800,000
Weighted average period			11 months 12 days
Intrinsic value, common stock price			$ 2.02	$ 3.30
Weighted Average Grant Date Fair Value Per Share, Granted			$ 2.04	$ 4.03
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			414,000	354,000
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	287,000
Restricted shares to vest upon milestone achievement			45,000
Amended and Restated Equity Incentive Plan 2013 [Member]
Stock-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for issuance	4,786,425
Increase in number of shares of common stock reserved under the plan	500,000
Award plan expiration year	2026
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			1,276,425
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			628,801
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%
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					300,000
Options available for future grant					928,801
One-Time Option Exchange Program [Member]
Stock-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of stock options exchanged		703,500
Number of stock options exchanged, outstanding		527,624
Number of stock options exchange percentage		75.00%
Options granted, vesting period		3 years
Stock options weighted average exercise price		$ 3.04
Incremental compensation expense during period under option exchange		$ 4,700
Unrecognized compensation costs		$ 141,000
Weighted average period		3 years