Equity - Series A Convertible Preferred Stock Converted and Outstanding, Number of Common Shares Issued and Issuable Upon Conversion of Series A Convertible Preferred Stock (Detail) - shares	12 Months Ended
	Dec. 31, 2017	Mar. 22, 2017
Class Of Stock [Line Items]
Series A Convertible Preferred Stock	5,000
Series A Convertible Preferred Stock Outstanding	5,000
Number of Common Shares Issuable Pursuant to Series A Convertible Stock Outstanding	18,274,000
Series A convertible preferred stock
Class Of Stock [Line Items]
Series A Convertible Preferred Stock	15,245,000	15,245
Converted to Common Shares	(9,928,000)
Series A Convertible Preferred Stock Outstanding	5,317,000
Number of Common Shares Issued Pursuant to Conversion of Series A Convertible Preferred Stock	4,963,702,000
Number of Common Shares Issuable Pursuant to Series A Convertible Stock Outstanding	2,658,670,000
Series A convertible preferred stock | Directors and Officers
Class Of Stock [Line Items]
Series A Convertible Preferred Stock	3,561,000
Converted to Common Shares	(2,537,000)
Series A Convertible Preferred Stock Outstanding	1,024,000
Number of Common Shares Issued Pursuant to Conversion of Series A Convertible Preferred Stock	1,268,499,000
Number of Common Shares Issuable Pursuant to Series A Convertible Stock Outstanding	511,997,000
Series A convertible preferred stock | Others
Class Of Stock [Line Items]
Series A Convertible Preferred Stock	11,684,000
Converted to Common Shares	(7,391,000)
Series A Convertible Preferred Stock Outstanding	4,293,000
Number of Common Shares Issued Pursuant to Conversion of Series A Convertible Preferred Stock	3,695,203,000
Number of Common Shares Issuable Pursuant to Series A Convertible Stock Outstanding	2,146,673,000