Summary of Significant Accounting Policies - Additional Information (Detail) |
9 Months Ended | |
|---|---|---|
|
Sep. 30, 2018
USD ($)
Segment
Institution
|
Dec. 31, 2017
USD ($)
Institution
|
|
| Summary Of Significant Accounting Policies [Line Items] | ||
| Number of operating segment | Segment | 1 | |
| Significant uncertain tax positions | $ | $ 0 | $ 0 |
| Number of principal financial institutions in cash deposit | Institution | 2 | 2 |
| Minimum [Member] | ||
| Summary Of Significant Accounting Policies [Line Items] | ||
| Furniture and equipment estimated useful lives | 3 years | |
| Maximum [Member] | ||
| Summary Of Significant Accounting Policies [Line Items] | ||
| Furniture and equipment estimated useful lives | 7 years |