Summary of Information with Regard to Outstanding Warrants Issued in Connection with Equity and Debt Financing and Consultants (Parenthetical) (Detail)	12 Months Ended
	Dec. 31, 2019 $ / shares
February 12, 2009 Series B-1 Transaction
Equity [Line Items]
Warrant issuance date	Feb. 12, 2009
Warrant issued price per share	$ 3.00
May 13, 2009 Series B-2 Transaction
Equity [Line Items]
Warrant issuance date	May 13, 2009
Warrant issued price per share	$ 3.00
June 30, 2009 Series B-2 Transaction
Equity [Line Items]
Warrant issuance date	Jun. 30, 2009
Warrant issued price per share	$ 3.00
August 12, 2009 Series B-2 Transaction
Equity [Line Items]
Warrant issuance date	Aug. 12, 2009
Warrant issued price per share	$ 3.00
September 30, 2009 Series B-2 Transaction
Equity [Line Items]
Warrant issuance date	Sep. 30, 2009
Warrant issued price per share	$ 3.00
November 4, 2009 Series B-2 Transaction
Equity [Line Items]
Warrant issuance date	Nov. 04, 2009
Warrant issued price per share	$ 3.00
December 8, 2009 Series B-2 Transaction
Equity [Line Items]
Warrant issuance date	Dec. 08, 2009
Warrant issued price per share	$ 3.00
January 29, 2010 Series B-2 Transaction
Equity [Line Items]
Warrant issuance date	Jan. 29, 2010
Warrant issued price per share	$ 3.00
March 8, 2010 Series B-2 Transaction
Equity [Line Items]
Warrant issuance date	Mar. 08, 2010
Warrant issued price per share	$ 3.00
April 30, 2010 Series B-2 Transaction
Equity [Line Items]
Warrant issuance date	Apr. 30, 2010
Warrant issued price per share	$ 3.00
May 10, 2010 Series B-2 Transaction
Equity [Line Items]
Warrant issuance date	May 10, 2010
Warrant issued price per share	$ 3.00
November 25, 2015 Offering Warrants
Equity [Line Items]
Warrant issuance date	Nov. 25, 2015
September 22, 2016 Series B-3 Transaction
Equity [Line Items]
Warrant issuance date	Sep. 22, 2016
Warrant issued price per share	$ 3.00
September 29, 2016 Series B-3 Transaction
Equity [Line Items]
Warrant issuance date	Sep. 29, 2016
Warrant issued price per share	$ 3.00
December 22, 2016 Private Placement Warrants
Equity [Line Items]
Warrant issuance date	Dec. 22, 2016
December 23, 2016 Series B-3 Transaction
Equity [Line Items]
Warrant issuance date	Dec. 23, 2016
Warrant issued price per share	$ 3.00
December 28, 2016 Private Placement Warrants
Equity [Line Items]
Warrant issuance date	Dec. 28, 2016
February 27, 2017 Private Placement Warrants
Equity [Line Items]
Warrant issuance date	Feb. 27, 2017
December 19, 2017 Line of Credit Warrants
Equity [Line Items]
Warrant issuance date	Dec. 19, 2017
May 23, 2019 Rights offering warrants
Equity [Line Items]
Warrant issuance date	May 23, 2019