Summary of Significant Accounting Policies - Summary of Property and Equipment Estimated Useful Lives (Detail) |
12 Months Ended |
|---|---|
Dec. 31, 2018 | |
| Computer Equipment [Member] | |
| Significant Accounting Policies [Line Items] | |
| Property, plant and equipment, useful life | 3 years |
| Software [Member] | |
| Significant Accounting Policies [Line Items] | |
| Property, plant and equipment, useful life | 3 years |
| Furniture and Fixtures [Member] | |
| Significant Accounting Policies [Line Items] | |
| Property, plant and equipment, useful life | 5 years |
| Leasehold Improvements [Member] | |
| Significant Accounting Policies [Line Items] | |
| Property, plant and equipment, useful life | Shorter of lease term or estimated useful life |