Stockholders' Equity - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions		1 Months Ended	3 Months Ended
	Mar. 31, 2019	Jan. 31, 2019	Mar. 31, 2019
Underwritten Offering [Member]
Stockholders Equity [Line Items]
Shares of common stock issued		23,000,000
Proceeds from issuance of common and convertible preferred stock, gross		$ 20.0
Proceeds from issuance of common and convertible preferred stock, net		$ 18.6
Underwritten Offering [Member] | Series E Convertible Preferred Stock [Member]
Stockholders Equity [Line Items]
Preferred stock, shares issued		17,000
Shares issued upon conversion		1,000
Numbers of shares converted			7,000
Preferred stock, shares outstanding	10,000		10,000
Underwritten Offering [Member] | Series E Convertible Preferred Stock [Member] | Maximum [Member]
Stockholders Equity [Line Items]
Percentage of outstanding common stock		9.98%
Underwritten Offering [Member] | Common Stock [Member]
Stockholders Equity [Line Items]
Price per common share		$ 0.50
Shares Issued upon conversion			7,000,000
Underwritten Offering [Member] | Preferred Stock [Member] | Series E Convertible Preferred Stock [Member]
Stockholders Equity [Line Items]
Price per common share		$ 500
Controlled Equity Offering Facilities [Member]
Stockholders Equity [Line Items]
Issuance of common stock, remaining offering value	$ 43.6		$ 43.6
Controlled Equity Offering Facilities [Member] | Common Stock [Member]
Stockholders Equity [Line Items]
Common stock, shares sold			0
CSPA [Member] | Aspire [Member] | Registration Rights Agreement [Member]
Stockholders Equity [Line Items]
Common stock, shares sold			0
Remaining purchase commitment	$ 10.9