Stockholders' Equity - Additional Information (Detail)																							9 Months Ended	12 Months Ended
	Dec. 31, 2016 shares	Dec. 30, 2016 shares	Dec. 29, 2016	Oct. 03, 2016 $ / shares shares	Sep. 30, 2016 USD ($) shares	Sep. 15, 2016 $ / shares shares	Aug. 29, 2016 $ / shares shares	Aug. 08, 2016 USD ($) $ / shares shares	May 06, 2016 $ / shares shares	Apr. 18, 2016 VicePresident $ / shares shares	Mar. 10, 2016 $ / shares shares	Feb. 26, 2016 $ / shares shares	Jan. 02, 2016 shares	Aug. 12, 2015 USD ($)	Jul. 13, 2015 $ / shares shares	Mar. 09, 2015 $ / shares shares	Jan. 02, 2015 $ / shares shares	Nov. 07, 2014 USD ($) $ / shares shares	Aug. 27, 2014 $ / shares shares	Jul. 22, 2014 USD ($) $ / shares shares	Jul. 13, 2014 $ / shares shares	Feb. 10, 2014 USD ($) $ / shares shares	Sep. 30, 2016 USD ($)	Dec. 31, 2016 USD ($) $ / shares shares	Dec. 31, 2015 USD ($) shares	Dec. 31, 2014 USD ($) shares	Jun. 23, 2015 shares	Dec. 31, 2013 shares
Stockholders Equity [Line Items]
Preferred stock, shares authorized	1,000,000																							1,000,000	1,000,000
Preferred stock, shares issued	88,494																							88,494	0
Preferred stock, shares outstanding	0																							0	0
Common stock, shares issued	67,565,951																							67,565,951	58,228,000
Common stock, shares outstanding	67,565,951																							67,565,951	58,228,000	37,422,753
Common stock, shares authorized	100,000,000																							100,000,000	100,000,000
Proceeds from equity offering, net of expenses | $								$ 9,500,000										$ 34,800,000		$ 11,500,000		$ 4,800,000		$ 9,520,000		$ 51,118,000
Dividend Declared | $																								0	$ 0
Deemed distribution to preferred shareholders, common stock at fair value | $																								2,184,000
Number of newly hired vice presidents | VicePresident										2
Chief Financial Officer
Stockholders Equity [Line Items]
Additional compensation expense related to modification | $																								$ 215,000
Share based compensation arrangement by share based payment award modification occurred to vest unvested options		294,205
Options exercise period		1 year	90 days
Share based compensation arrangement by share based payment award vested stock options		623,026
Chief Financial Officer | Vest on January 2, 2016
Stockholders Equity [Line Items]
Stock options granted																523,026
Option shares vested and exercised																130,757
Shares vested and exercisable date																Mar. 09, 2016
Shares vested and exercised consecutive term																35 months
Share based compensation arrangement by share Based payment award fair value price | $ / shares																$ 1.48
Expected term (years)																6 years 1 month 6 days
Volatility																88.79%
Risk-free interest rate																1.83%
Chief Financial Officer | CFO Grant Award Tranche Two
Stockholders Equity [Line Items]
Stock options granted																348,684
Shares vested and exercisable date																Mar. 09, 2025
Share based compensation arrangement by share Based payment award fair value price | $ / shares																$ 1.70
Expected term (years)																10 years
Volatility																87.87%
Risk-free interest rate																2.19%
Option shares vested and exercised	100,000
Chief Executive Officer
Stockholders Equity [Line Items]
Shares vested and exercised consecutive term															36 months
Stock Options | New Employees
Stockholders Equity [Line Items]
Options vesting description																								For the 25,000 options awarded to new employees, 25% vest on February 6, 2018 and the remainder ratably over the 36-month period, commencing on March 6, 2018.
Stock Options | Vice Presidents
Stockholders Equity [Line Items]
Stock options granted				125,000		250,000				325,000
Awards issued per share | $ / shares				$ 1.72		$ 1.78				$ 1.43
Options expiration period				10 years		10 years				10 years
Share-based Compensation Arrangement by Share-based Payment Award, Monthly Ratable Award Vesting Period						36 months				36 months
Share Based Compensation Arrangement By Share Based Payment Award, Vesting Commencement Date						Sep. 15, 2017				Apr. 18, 2017
Percentage of time based vesting for options						75.00%				75.00%
Percentage of performance based vesting in options granted				50.00%
Stock Options | Vice Presidents | Awards Vesting on April 18, 2017
Stockholders Equity [Line Items]
Vesting percentage										25.00%
Stock Options | Vice Presidents | Vest on February 26, 2018
Stockholders Equity [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Date						Sep. 15, 2017				Apr. 18, 2017
Stock Options | Vice Presidents | Awards Vesting on September 15, 2017
Stockholders Equity [Line Items]
Vesting percentage						25.00%
Stock Options | Vice Presidents | Awards Vesting on October 3, 2017
Stockholders Equity [Line Items]
Vesting percentage				25.00%
Stock Options | Vice Presidents | Time Based Vesting Commencing October 3, 2017
Stockholders Equity [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Monthly Ratable Award Vesting Period				36 months
Share Based Compensation Arrangement By Share Based Payment Award, Vesting Commencement Date				Oct. 03, 2017
Percentage of time based vesting for options				75.00%
Stock Options | Non-Employee Directors
Stockholders Equity [Line Items]
Stock options granted									597,757
Awards issued per share | $ / shares									$ 1.41
Options expiration period									10 years
Share-based Compensation Arrangement by Share-based Payment Award, Monthly Ratable Award Vesting Period									12 months
Share Based Compensation Arrangement By Share Based Payment Award, Vesting Commencement Date									Jun. 06, 2016
Stock Options | Senior Director
Stockholders Equity [Line Items]
Stock options granted							60,000
Awards issued per share | $ / shares							$ 1.65
Options expiration period							10 years
Share-based Compensation Arrangement by Share-based Payment Award, Monthly Ratable Award Vesting Period							48 months
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Date							Sep. 29, 2016
Stock Options | President And Chief Executive Officer
Stockholders Equity [Line Items]
Stock options granted																								1,400,000
Options expiration period																								10 years
Range of exercise price, lower limit | $ / shares																								$ 1.44
Range of exercise price, upper limit | $ / shares																								$ 1.45
Non-qualified Stock Options
Stockholders Equity [Line Items]
Options available for future grants																					172,282
Exercise Price of Stock Options | $ / shares																	$ 2.64
Stock options granted at an exercise price | $ / shares																					$ 1.98
Non-qualified Stock Options | Officers
Stockholders Equity [Line Items]
Stock options granted																	1,365,702
Options expiration period																	10 years
Options vesting description																								(i) as to 50% of the options, one-fourth on the one year anniversary of the grant date and the remaining three-fourths, ratably over the next 36 month period, commencing on the thirteenth month from grant date over a requisite service period of four years, and (ii) as to 50% of the options, upon achievement of specific annual Company performance criteria with a requisite service period of one year.
Non-qualified Stock Options | Consultants
Stockholders Equity [Line Items]
Stock options granted																	86,000
Options expiration period																	5 years
Non-qualified Stock Options | Chief Financial Officer
Stockholders Equity [Line Items]
Stock options granted																871,710
Options expiration period																10 years
Stock options granted at an exercise price | $ / shares																$ 1.99
Non-qualified Stock Options | Chief Executive Officer
Stockholders Equity [Line Items]
Stock options granted															870,000
Options expiration period															10 years
Share-based Compensation Arrangement by Share-based Payment Award, Monthly Ratable Award Vesting Period															4 years
Stock options outstanding	435,000																							435,000
Exercise Price of Stock Options | $ / shares															$ 1.64
Stock options granted at an exercise price | $ / shares															$ 1.64
Restricted Stock Units (RSUs)
Stockholders Equity [Line Items]
Options available for future grants																					37,879,000
Exercise Price of Stock Options | $ / shares																					$ 1.98
Granted																								906,773		36,868
Outstanding shares of RSUs	418,511																							418,511		36,868
Restricted Stock Units (RSUs) | Employees and Consultants
Stockholders Equity [Line Items]
Awards issued per share | $ / shares												$ 0.86
Granted												140,000
Restricted Stock Units (RSUs) | Employees and Consultants | Vest on January 2, 2016
Stockholders Equity [Line Items]
Vesting percentage												25.00%
Restricted Stock Units (RSUs) | Employees and Consultants | Vest on February 26, 2018
Stockholders Equity [Line Items]
Vesting percentage												25.00%
Restricted Stock Units (RSUs) | Employees and Consultants | Vest on July 1, 2016
Stockholders Equity [Line Items]
Awards issued per share | $ / shares												$ 0.86
Granted												388,500
Restricted Stock Units (RSUs) | Employees and Consultants | Vest on February 26, 2019
Stockholders Equity [Line Items]
Vesting percentage												25.00%
Restricted Stock Units (RSUs) | Employees and Consultants | Vest on February 26, 2020
Stockholders Equity [Line Items]
Vesting percentage												25.00%
Restricted Stock Units (RSUs) | Non-Employee Directors | Vest on May 6, 2017
Stockholders Equity [Line Items]
Awards issued per share | $ / shares									$ 1.41
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Date									May 06, 2017
Granted									248,750
Restricted Stock Units (RSUs) | President And Chief Executive Officer
Stockholders Equity [Line Items]
Awards issued per share | $ / shares												$ 0.86
Granted												59,523
Maximum performance bonus awarded | $																							$ 100,000
Restricted Stock Units (RSUs) | President And Chief Executive Officer | Vesting on March 30, 2016
Stockholders Equity [Line Items]
Vesting percentage												50.00%
Restricted Stock Units (RSUs) | President And Chief Executive Officer | Vesting on February 18, 2017
Stockholders Equity [Line Items]
Vesting percentage												50.00%
Restricted Stock Units (RSUs) | Four Independent Director
Stockholders Equity [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Monthly Ratable Award Vesting Period																			12 months
Granted																			36,868
Share-based compensation arrangement by share-based payment award, equity instruments other than options, value per share | $ / shares																			$ 2.17
Restricted Stock Units (RSUs) | Prior Chief Executive Officer
Stockholders Equity [Line Items]
Outstanding shares of RSUs	0																							0
Options Vesting And Becoming Exercisable Each Month | Chief Financial Officer | Vest on January 2, 2016
Stockholders Equity [Line Items]
Option shares vested and exercised																10,896
Options Vesting And Becoming Exercisable Each Month | Chief Executive Officer
Stockholders Equity [Line Items]
Option shares vested and exercised															18,125
Thirty Six Month Anniversary | Chief Financial Officer | Vest on January 2, 2016
Stockholders Equity [Line Items]
Option shares vested and exercised																10,909
Shares vested and exercisable date																Mar. 09, 2019
Ten Year Anniversary | Chief Financial Officer | CFO Grant Award Tranche Two
Stockholders Equity [Line Items]
Option shares vested and exercised																											100,000
One Year Anniversary | Chief Executive Officer
Stockholders Equity [Line Items]
Option shares vested and exercised															217,500
2002 Stock Incentive Plan
Stockholders Equity [Line Items]
Plan expiration date																								May 05, 2019
Common stock authorized for issuance under the 2002 Plan	15,550,000																							15,550,000
Common stock issued pursuant to options exercised																								3,557,068
Options outstanding	7,030,074																							7,030,074
Options available for future grants	4,962,858																							4,962,858
Stock options outstanding	6,612,000																							6,612,000	4,493,000	3,475,000		4,441,000
Expected term (years)																								5 years 11 months 16 days	5 years 9 months 18 days	3 years 9 months 29 days
Volatility																								86.00%	90.00%	94.00%
Risk-free interest rate																								1.39%	1.64%	1.66%
2002 Stock Incentive Plan | Non-qualified Stock Options | Officers And Consultant
Stockholders Equity [Line Items]
Options available for future grants																									122,038
Stock options granted													488,170
Two Thousand Sixteen Compensation Plan | Stock Options | Employees and Consultants
Stockholders Equity [Line Items]
Stock options granted												295,000
Awards issued per share | $ / shares												$ 0.86
Options expiration period												10 years
Two Thousand Sixteen Compensation Plan | Stock Options | Existing Employees
Stockholders Equity [Line Items]
Stock options granted												185,000
Share-based Compensation Arrangement by Share-based Payment Award, Monthly Ratable Award Vesting Period												48 months
Two Thousand Sixteen Compensation Plan | Stock Options | New Employees
Stockholders Equity [Line Items]
Stock options granted												110,000
Share-based Compensation Arrangement by Share-based Payment Award, Monthly Ratable Award Vesting Period												36 months
Two Thousand Sixteen Compensation Plan | Stock Options | New Employees | Vest on January 2, 2016
Stockholders Equity [Line Items]
Vesting percentage												25.00%
April 18, 2016 Compensation Plan | Stock Options | Vice Presidents
Stockholders Equity [Line Items]
Stock options outstanding	243,750																							243,750
August 29, 2016 Compensation Plan | Stock Options | Senior Director
Stockholders Equity [Line Items]
Stock options outstanding	60,000																							60,000
September 15, 2016 Compensation Plan | Stock Options | Vice Presidents
Stockholders Equity [Line Items]
Stock options outstanding	250,000																							250,000
October 3, 2016 Compensation Plan | Stock Options | Vice Presidents
Stockholders Equity [Line Items]
Stock options outstanding	125,000																							125,000
Two Thousand Fifteen Compensation Plan | Non-qualified Stock Options | Officers And Consultant
Stockholders Equity [Line Items]
Decrease in fair value awards | $														$ 661,000
Additional compensation expense related to modification | $																									$ 154,000
Two Thousand Fifteen Compensation Plan | Non-qualified Stock Options | Officers And Consultant | Vest on January 2, 2016
Stockholders Equity [Line Items]
Vesting percentage													80.00%
Two Thousand Fifteen Compensation Plan | Restricted Stock Units (RSUs) | Chief Financial Officer
Stockholders Equity [Line Items]
Awards issued per share | $ / shares											$ 1.23
Granted											70,000
Warrants
Stockholders Equity [Line Items]
Warrants issued to purchase common stock								2,035,398										9,205,862
Class of Warrant or Right, Exercise Price of Warrants or Rights | $ / shares								$ 2.00										$ 4.00
Granted																								2,035,398		9,205,862
Outstanding shares of RSUs	11,406,260																							11,406,260	10,093,836	10,093,836		1,697,974
2016 Common Stock Issuance
Stockholders Equity [Line Items]
Issuance of stock, net, shares								88,494
Warrants issued to purchase common stock								2,035,398
Class of Warrant or Right, Exercise Price of Warrants or Rights | $ / shares								$ 2.00
Conversion of stock, each shares issued								100
Stock conversion, price | $ / shares								$ 1.13
Conversion of stock, shares issued					8,849,400
Proceeds from equity offering, gross | $					$ 10,000,000
Proceeds from equity offering, net of expenses | $					9,500,000
Payments of stock issuance costs | $					$ 500,000
Warrants exercisable								Feb. 08, 2017
Warrants issued for term								5 years
2014 Common Stock Issuances
Stockholders Equity [Line Items]
Issuance of stock, net, shares																		14,162,873
Warrants issued to purchase common stock								2,035,398										9,205,862
Class of Warrant or Right, Exercise Price of Warrants or Rights | $ / shares								$ 2.00										$ 4.00
Conversion of stock, each shares issued								100
Stock conversion, price | $ / shares								$ 1.13
Conversion of stock, shares issued																								8,849,400
Proceeds from equity offering, gross | $																		$ 35,000,000
Proceeds from equity offering, net of expenses | $																		34,800,000						$ 9,500,000
Payments of stock issuance costs | $																		$ 235,000						500,000
Warrants exercisable																		May 07, 2015
Warrants issued for term																		3 years
Common stock issued, price per share | $ / shares																		$ 2.39
Proceeds from equity offering, gross | $																								10,000,000
Deemed distribution to preferred shareholders, common stock at fair value | $																								1,100,000
2014 Common Stock Issuances | Beneficial Conversion
Stockholders Equity [Line Items]
Proceeds from equity offering, gross | $																								$ 1,100,000
2014 Common Stock Issuances | Warrants
Stockholders Equity [Line Items]
Proceeds from equity offering, gross | $																							$ 1,100,000
July 2014 Private Placement
Stockholders Equity [Line Items]
Issuance of stock, net, shares																				6,250,000
Proceeds from equity offering, gross | $																				$ 12,000,000
Proceeds from equity offering, net of expenses | $																				11,500,000
Payments of stock issuance costs | $																				$ 462,000
Common stock issued, price per share | $ / shares																				$ 1.92
February 2014 Subscription Agreement
Stockholders Equity [Line Items]
Issuance of stock, net, shares																						1,945,525
Proceeds from equity offering, gross | $																						$ 5,000,000
Proceeds from equity offering, net of expenses | $																						4,800,000
Payments of stock issuance costs | $																						$ 188,000
Common stock issued, price per share | $ / shares																						$ 2.57
Maximum
Stockholders Equity [Line Items]
Preferred stock, shares authorized	1,000,000																							1,000,000
Maximum | Stock Options | President And Chief Executive Officer
Stockholders Equity [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Monthly Ratable Award Vesting Period																								4 years
Minimum | Stock Options | President And Chief Executive Officer
Stockholders Equity [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Monthly Ratable Award Vesting Period																								2 years
Series B Junior Participating Cumulative Preferred Stock
Stockholders Equity [Line Items]
Preferred stock, shares authorized	500,000																							500,000