Value of input used to measure outstanding warrant and right embodying unconditional obligation requiring redemption by transferring asset at specified or determinable date or upon event certain to occur.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (bbb)(2)
-URI http://asc.fasb.org/extlink&oid=99377789&loc=d3e19207-110258

Name:	us-gaap_WarrantsAndRightsOutstandingMeasurementInput
Namespace Prefix:	us-gaap_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	instant

Assumptions Used in the Black-Scholes Option Pricing Model to Determine the Fair Value of the Common Stock Warrants (Parenthetical) (Detail)	Sep. 30, 2018 $ / shares	Sep. 30, 2018 $ / shares	Dec. 31, 2017 $ / shares	Dec. 31, 2017 $ / shares
Exercise Price
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Valuation assumptions measurement input	0.64	55.00	0.64	55.00