Warrants (Detail)	6 Months Ended
	Jun. 30, 2019 $ / shares shares
Warrants Outstanding Rollforward [Roll Forward]
Warrants Outstanding, Beginning Balance (in shares)	274,524
Warrants Issued (in shares)	0
Warrants Exercised (in shares)	0
Warrants Expired (in shares)	0
Warrants Outstanding, Ending Balance (in shares)	274,524
Hercules - June 2014
Warrants Outstanding Rollforward [Roll Forward]
Warrants Outstanding, Beginning Balance (in shares)	1,583
Warrants Issued (in shares)	0
Warrants Exercised (in shares)	0
Warrants Expired (in shares)	0
Warrants Outstanding, Ending Balance (in shares)	1,583
Exercise Price (in USD per share) | $ / shares	$ 176.80
Expiration Date	Jan. 27, 2020
Hercules - June 2015
Warrants Outstanding Rollforward [Roll Forward]
Warrants Outstanding, Beginning Balance (in shares)	2,035
Warrants Issued (in shares)	0
Warrants Exercised (in shares)	0
Warrants Expired (in shares)	0
Warrants Outstanding, Ending Balance (in shares)	2,035
Exercise Price (in USD per share) | $ / shares	$ 147.40
Expiration Date	Jun. 23, 2020
Trinity - September 2018
Warrants Outstanding Rollforward [Roll Forward]
Warrants Outstanding, Beginning Balance (in shares)	75,000
Warrants Issued (in shares)	0
Warrants Exercised (in shares)	0
Warrants Expired (in shares)	0
Warrants Outstanding, Ending Balance (in shares)	75,000
Exercise Price (in USD per share) | $ / shares	$ 3.59
Expiration Date	Sep. 25, 2025
Private Investment in Public Equity (PIPE) | Series B
Warrants Outstanding Rollforward [Roll Forward]
Warrants Outstanding, Beginning Balance (in shares)	195,906
Warrants Issued (in shares)	0
Warrants Exercised (in shares)	0
Warrants Expired (in shares)	0
Warrants Outstanding, Ending Balance (in shares)	195,906
Exercise Price (in USD per share) | $ / shares	$ 31.00
Expiration Date	Aug. 19, 2021