Embedded Derivatives - Assumptions Used to Estimate Fair Value of Embedded Redemption and Conversion Derivative Financial Instruments Embedded (Detail) - Level 3 [Member]	Jun. 30, 2018
Volatility [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Estimated fair value assumptions	93.5
Default Factor [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Estimated fair value assumptions	33.0
Risk Free Rate Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Estimated fair value assumptions	2.1