Stock-Based Compensation and Warrants - Additional Information (Detail)			1 Months Ended				3 Months Ended		6 Months Ended
	May 20, 2015 shares	May 14, 2015	Jun. 30, 2018 USD ($) $ / shares shares	May 31, 2018 $ / shares shares	Mar. 31, 2018 $ / shares shares	Dec. 31, 2013 $ / shares shares	Jun. 30, 2018 USD ($) $ / shares shares	Jun. 30, 2017 USD ($)	Jun. 30, 2018 USD ($) IncentivePlan $ / shares shares	Jun. 30, 2017 USD ($)	Jun. 30, 2014 $ / shares shares	Dec. 31, 2017 shares
Share-based Compensation Arrangement by Share-based Payment Award and Warrants [Line Items]
Number of equity incentive plans | IncentivePlan									2
Total number of options outstanding			283,259				283,259		283,259			288,129
Unrecognized compensation cost related to unvested stock-based compensation grants | $			$ 1,200,000				$ 1,200,000		$ 1,200,000
Weighted-average remaining recognition period									2 years 7 months 6 days
Stock-based compensation | $									$ 656,000	$ 760,000
Warrants issued, exercise price | $ / shares				$ 10.7258		$ 330.40
Warrant, exercisable term				5 years
Warrant issued, shares of common stock called by warrant				982,080
Warrant issued, shares of common stock called by all warrant issued to date				1,282,832
Placement Agent [Member] | June Purchase Agreement [Member]
Share-based Compensation Arrangement by Share-based Payment Award and Warrants [Line Items]
Warrants issued, exercise price | $ / shares			$ 12.568				$ 12.568		$ 12.568
Warrant, exercisable term			5 years
Warrant issued, shares of common stock called by warrant			69,617				69,617		69,617
Series D Redeemable Convertible Preferred Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award and Warrants [Line Items]
Warrants issued, exercise price | $ / shares											$ 363.20
Warrant, exercisable term											5 years
Warrant issued, shares of common stock called by warrant											61,397
Series D Redeemable Convertible Preferred Stock [Member] | Placement Agent [Member]
Share-based Compensation Arrangement by Share-based Payment Award and Warrants [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 and Warrants [Line Items]
Warrant issued, shares of common stock called by warrant						3,784
Warrant, exercisable term						5 years
2015 Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award and Warrants [Line Items]
Total number of shares reserved for issuance under plan			90,044				90,044		90,044
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									6,324
First offering period, start date		May 14, 2015
First offering period, end date		Feb. 01, 2016
Stock-based compensation | $							$ 400	$ 1,600	$ 2,000	$ 6,000
Private Placement [Member]
Share-based Compensation Arrangement by Share-based Payment Award and Warrants [Line Items]
Warrants issued, exercise price | $ / shares					$ 45.75
Warrant, exercisable term					5 years
Private Placement [Member] | June Purchase Agreement [Member]
Share-based Compensation Arrangement by Share-based Payment Award and Warrants [Line Items]
Warrant issued, shares of common stock called by warrant			1,392,345				1,392,345		1,392,345
Warrants issued, exercise price | $ / shares			$ 9.94				$ 9.94		$ 9.94
Warrant, exercisable term			5 years 6 months
Warrant issued, percentage of shares of common stock sold			100.00%
Warrants issued, purchase price of warrants per share | $ / shares			$ 0.125				0.125		0.125
Private Placement [Member] | Placement Agent [Member]
Share-based Compensation Arrangement by Share-based Payment Award and Warrants [Line Items]
Warrants issued, exercise price | $ / shares					$ 41.5625
Warrant issued, shares of common stock called by warrant					15,038
Maximum [Member] | Private Placement [Member]
Share-based Compensation Arrangement by Share-based Payment Award and Warrants [Line Items]
Warrant issued, shares of common stock called by warrant					300,752
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award and Warrants [Line Items]
Warrants issued, exercise price | $ / shares			$ 8.322				$ 8.322		$ 8.322
2015 Omnibus Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award and Warrants [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		483,807				483,807		483,807
Options vesting period	4 years
Common stock available for future grant			268,443				268,443		268,443
Total number of options outstanding			215,362				215,362		215,362
2015 Omnibus Equity Incentive Plan [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award and Warrants [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 and Warrants [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 and Warrants [Line Items]
Total number of shares reserved for issuance under plan	10,637
Total number of options outstanding			67,897				67,897		67,897