Stock-Based Compensation and Warrants - Additional Information (Detail)				1 Months Ended			3 Months Ended			6 Months Ended
	Mar. 28, 2019 shares	May 20, 2015 shares	May 14, 2015	Jun. 30, 2019 USD ($) $ / shares shares	Apr. 30, 2019 USD ($) $ / shares shares	Dec. 31, 2013 $ / shares shares	Jun. 30, 2019 USD ($) $ / shares shares	Sep. 30, 2018	Jun. 30, 2018 USD ($)	Jun. 30, 2019 USD ($) IncentivePlan $ / shares shares	Jun. 30, 2018 USD ($) shares	Dec. 31, 2018 shares	Jun. 30, 2014 $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of equity incentive plans | IncentivePlan										2
Total number of options outstanding				710,718			710,718			710,718		530,044
Unrecognized compensation cost related to unvested stock-based compensation grants | $				$ 1,400,000			$ 1,400,000			$ 1,400,000
Weighted-average remaining recognition period										2 years 2 months 12 days
Options granted										184,071	44,910
Stock-based compensation | $										$ 811,000	$ 656,000
Number of warrant to purchase common stock issued				4,469,040			4,469,040			4,469,040
Warrants issued, exercise price | $ / shares				$ 8.48			$ 8.48			$ 8.48
Stock price | $ / shares				32.52			32.52			32.52
Black Scholes Merton Model [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock price | $ / shares				$ 8.20			$ 8.20			$ 8.20
Service Warrants [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Warrants issued, exercise price | $ / shares					$ 6.18
Warrant issued, shares of common stock called by warrant					45,154
Warrants vesting period					12 months
Warrant, exercisable term					5 years
Fair value of Warrants | $					$ 224,000
Compensation expense associated with Warrants, term										1 year
Compensation expense associated with Warrants | $							$ 44,000
Performance Warrants [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Warrants issued, exercise price | $ / shares					$ 6.18
Warrant issued, shares of common stock called by warrant					100,000
Warrant, exercisable term					5 years
Fair value of Warrants | $					$ 497,000
Compensation expense associated with Warrants | $										$ 0
Service and Performance Warrants [Member] | Black Scholes Merton Model [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock price | $ / shares					$ 6.18
Service and Performance Warrants [Member] | Black Scholes Merton Model [Member] | Volatility [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Warrants, measurement input					1.125
Service and Performance Warrants [Member] | Black Scholes Merton Model [Member] | Risk-Free Rate [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Warrants, measurement input					0.0237
June 2019 Purchase Agreement [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of warrant to purchase common stock issued				1,564,054			1,564,054			1,564,054
Placement Agent [Member] | June 2019 Purchase Agreement [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Warrants issued, exercise price | $ / shares				$ 6.2938			$ 6.2938			$ 6.2938
Warrant issued, shares of common stock called by warrant				74,479			74,479			74,479
Warrant, exercisable term				5 years
Series D Redeemable Convertible Preferred Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Warrant issued, shares of common stock called by warrant													63,071
Number of warrants expired	1,759						61,312
Series D Redeemable Convertible Preferred Stock [Member] | Placement Agent [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Warrants issued, exercise price | $ / shares													$ 268.80
Warrant issued, shares of common stock called by warrant													1,674
Mahyco International [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Warrants issued, exercise price | $ / shares						$ 330.40
Warrant issued, shares of common stock called by warrant						3,784
Warrant, expiration date						Dec. 11, 2018
Investor [Member] | Series D Redeemable Convertible Preferred Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Warrants issued, exercise price | $ / shares													$ 363.20
Warrant issued, shares of common stock called by warrant													61,397
2015 Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total number of shares reserved for issuance under plan				108,864			108,864			108,864
Percentage in payroll deductions to acquire shares of common stock			15.00%
Purchase plan offering period			6 months
Employees are able to purchase company's common stock on first trading day of offering period, percentage			85.00%
Issuance of common stock pursuant to employee stock purchase plan										9,353
Stock-based compensation | $							$ 3,800		$ 400	$ 8,100	$ 1,600
Purchase Agreement [Member] | March 2018 Purchase Agreement [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of warrant to purchase common stock issued				1,297,870			1,297,870			1,297,870
Purchase Agreement [Member] | March 2018 Purchase Agreement [Member] | Purchase Price of $10.7258 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of warrant to purchase common stock issued				1,282,832			1,282,832			1,282,832
Warrants issued, purchase price of warrants per share | $ / shares				$ 10.7258			$ 10.7258			$ 10.7258
Purchase Agreement [Member] | March 2018 Purchase Agreement [Member] | Exercise Price of $41.5625 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of warrant to purchase common stock issued				15,038			15,038			15,038
Warrants issued, exercise price | $ / shares				$ 41.5625			$ 41.5625			$ 41.5625
Purchase Agreement [Member] | June 2018 Offering [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of warrant to purchase common stock issued				1,461,962			1,461,962			1,461,962
Purchase Agreement [Member] | June 2018 Offering [Member] | Purchase Price of $9.94 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of warrant to purchase common stock issued				1,392,345			1,392,345			1,392,345
Warrants issued, purchase price of warrants per share | $ / shares				$ 9.94			$ 9.94			$ 9.94
Purchase Agreement [Member] | June 2018 Offering [Member] | Exercise Price of $12.568 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of warrant to purchase common stock issued				69,617			69,617			69,617
Warrants issued, exercise price | $ / shares				$ 12.568			$ 12.568			$ 12.568
Purchase Agreement [Member] | June 2019 Purchase Agreement [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Warrants issued, exercise price | $ / shares				$ 5.00			$ 5.00			$ 5.00
Warrant issued, shares of common stock called by warrant				1,489,575			1,489,575			1,489,575
Warrants issued, purchase price of warrants per share | $ / shares				$ 0.125			$ 0.125			$ 0.125
Warrant, exercisable term				5 years 6 months
Class of warrant or right, issued percentage in connection with common stock sold				100.00%
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Warrant, expiration date										2024-12
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Warrant, expiration date										2023-03
2015 Omnibus Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Terms under the plan										The 2015 Plan became effective in May 2015 and all shares that were reserved, but not issued, under the 2006 Plan were assumed by the 2015 Plan. Upon effectiveness, the 2015 Plan had 154,387 shares of common stock reserved for future issuance, which included 10,637 shares under the 2006 Plan that were transferred to and assumed by the 2015 Plan. The 2015 Plan provides for automatic annual increases in shares available for grant. In addition, shares subject to awards under the 2006 Plan that are forfeited or canceled will be added to the 2015 Plan.
Total number of shares reserved for issuance under plan		154,387		659,786			659,786			659,786
Options vesting period		4 years						2 years
Additional shares authorized for issuance under the plan				120,000
Common stock available for future grant				10,397			10,397			10,397
Total number of options outstanding				649,389			649,389			649,389
2015 Omnibus Equity Incentive Plan [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options exercisable period		10 years
2015 Omnibus Equity Incentive Plan [Member] | Share-based Compensation Award, Tranche One [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options vesting percentage at end of one year		25.00%
2006 Stock Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total number of shares reserved for issuance under plan		10,637
Total number of options outstanding				61,329			61,329			61,329