Financial Instruments - Roll-Forward of Fair Value Measurements Using Significant Unobservable Inputs (Level 3) for Warrants (Detail) - Outstanding Warrants [Member] $ in Thousands |
12 Months Ended |
|---|---|
|
Dec. 31, 2016
USD ($)
| |
| Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items] | |
| Beginning Balance | $ 649 |
| Settlements from exercise | (202) |
| Expense for the period | 557 |
| Ending Balance | $ 1,004 |