Fair Value Measurement - Summary of Fair Value Measured on Recurring Basis (Detail) $ in Thousands	Dec. 31, 2016 USD ($)
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Derivative asset - embedded conversion feature	$ 80,651
Fair Value Measurements Recurring [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Derivative asset - embedded conversion feature	80,651
Fair Value Measurements Recurring [Member] | Level 3
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Derivative asset - embedded conversion feature	$ 80,651