Stockholders' Equity - Preferred Stock and Convertible Preferred Stock (Detail) - USD ($)	Jun. 30, 2017	Dec. 31, 2016
Non-Convertible Preferred Stock
Class of Stock [Line Items]
Value of preferred stock issued	$ 0	$ 0
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized (in shares)	5,000,000	5,000,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Series B Convertible Preferred Stock
Class of Stock [Line Items]
Value of preferred stock issued	$ 1	$ 1
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, shares issued (in shares)	500	500
Preferred stock, shares outstanding (in shares)	500	500
Preferred stock, shares designated (in shares)	147,000	147,000
Series D Convertible Preferred Stock
Class of Stock [Line Items]
Value of preferred stock issued	$ 14	$ 17
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, shares issued (in shares)	14,052.93	17,202.65
Preferred stock, shares outstanding (in shares)	14,052.93	17,202.65
Preferred stock, shares designated (in shares)	21,300	21,300
Series E Convertible Preferred Stock
Class of Stock [Line Items]
Value of preferred stock issued	$ 7	$ 0
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, shares issued (in shares)	7,000	0
Preferred stock, shares outstanding (in shares)	7,000	0
Preferred stock, shares designated (in shares)	7,000	0