Quarterly report pursuant to Section 13 or 15(d)

Capital Structure - Additional Information (Detail)

Capital Structure - Additional Information (Detail) - USD ($)								1 Months Ended	3 Months Ended	6 Months Ended	9 Months Ended		13 Months Ended
	Sep. 30, 2018	Aug. 03, 2018	Jul. 25, 2017	Jul. 27, 2016	Nov. 02, 2015	Jun. 12, 2015	Aug. 01, 2014	Aug. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Sep. 30, 2018	Sep. 30, 2017	Jun. 30, 2014	Dec. 31, 2017
Class of Stock [Line Items]
Common stock, shares authorized	200,000,000								200,000,000		200,000,000			200,000,000
Common stock, par value	$ 0.0001								$ 0.0001		$ 0.0001			$ 0.0001
Issuance costs allocated to warrants											$ 0	$ 905,014
Net proceeds from initial public offering							$ 35,000,000
Initial public offering, closing date											Aug. 01, 2014
Initial public offering, units description											In August 2014, the Company completed an initial public offering (“IPO”), raising net proceeds of $35.0 million after underwriting discounts, commissions and offering expenses payable by us, through the issuance and sale of our units, which consisted of one share of common stock, one Class A Warrant to purchase one share of common stock at an exercise price of $4.80 per share and one Class B Warrant to purchase one-half share of common stock at an exercise price of $4.00 per full share (“Units”).
Proceeds from exercise of warrants											$ 5,503
Number of warrants or rights outstanding	31,265,182								31,265,182		31,265,182			36,270,103
Common stock, voting rights											The holders of shares of common stock are entitled to one vote for each share of common stock held at all meetings of stockholders and written actions in lieu of meetings.
Dividends declared or paid	$ 0
8.00% Convertible Notes due May 31, 2015 [Member]
Class of Stock [Line Items]
Convertible Notes, principal amount													$ 15,000,000
Convertible Notes, interest rate													8.00%
Convertible Notes, due date													May 31, 2015
2016 Warrants [Member]
Class of Stock [Line Items]
Number of warrants or rights outstanding	14,000,000								14,000,000		14,000,000			14,000,000
2017 Warrants [Member]
Class of Stock [Line Items]
Number of warrants or rights outstanding	15,996,450								15,996,450		15,996,450			16,000,000
Private Placement [Member]
Class of Stock [Line Items]
Number of shares issued						4,728,128
Aggregate gross sales proceeds from common stock						$ 20,000,000
Net proceeds received						$ 18,300,000
Warrants to purchase shares of common stock	189,126					2,364,066			189,126		189,126
Warrant exercise price per share	$ 4.65					$ 8.00			$ 4.65		$ 4.65
Warrant expiration term						3 years
Warrant expiration date											Jun. 11, 2020
Initial Public Offering [Member]
Class of Stock [Line Items]
Conversion of Convertible Notes together with accrued and unpaid interest into common stock, shares							5,109,988
Follow-on Offering [Member]
Class of Stock [Line Items]
Number of shares issued		5,750,000	32,000,000	14,000,000
Aggregate gross sales proceeds from common stock		$ 11,500,000	$ 40,000,000	$ 35,000,000
Net proceeds received		$ 10,400,000	$ 37,100,000	$ 32,000,000
Warrants to purchase shares of common stock									0		3,550
Follow-on Offering [Member] \| CMPO Warrants [Member]
Class of Stock [Line Items]
Warrants to purchase shares of common stock			16,000,000	14,000,000
Follow-on Offering [Member] \| 2016 Warrants [Member]
Class of Stock [Line Items]
Warrant exercise price per share				$ 3.00
Warrant expiration term				5 years
Fair value of warrants				$ 18,600,000
Issuance costs allocated to warrants				$ 1,600,000
Follow-on Offering [Member] \| 2017 Warrants [Member]
Class of Stock [Line Items]
Warrant exercise price per share			$ 1.55
Warrant expiration term			5 years
Fair value of warrants			$ 12,400,000
Issuance costs allocated to warrants			$ 900,000
Note Warrants [Member]
Class of Stock [Line Items]
Warrant exercise price per share							$ 3.00
Warrant expiration term										5 years
Number of warrants or rights outstanding	692,858						3,321,416		692,858		692,858			3,315,878
Class of warrant or rights, expired								413,432		2,209,588
Class B Warrants [Member]
Class of Stock [Line Items]
Warrant expiration date											Nov. 02, 2015
Warrants exercised					4,812,328
Common stock shares issued upon exercise of warrants					2,406,164
Proceeds from exercise of warrants					$ 9,600,000
Class B Warrants [Member] \| Initial Public Offering [Member]
Class of Stock [Line Items]
Warrant exercise price per share							$ 4.00
Representative's Warrant [Member]
Class of Stock [Line Items]
Warrants to purchase shares of common stock	206,410								206,410		206,410
Warrant exercise price per share	$ 7.50								$ 7.50		$ 7.50
Warrant expiration date											Jul. 28, 2019
Class of warrant purchase percentage	3.00%								3.00%		3.00%
Warrant exercisable period											180 days
Number of warrants or rights outstanding	206,410								206,410		206,410			206,410
Class A Warrants [Member]
Class of Stock [Line Items]
Warrant expiration date											Feb. 01, 2017
Class A Warrants [Member] \| Initial Public Offering [Member]
Class of Stock [Line Items]
Warrant exercise price per share							$ 4.80