Balance Sheet Items - Additional Information (Detail) ft² in Thousands, $ in Millions |
12 Months Ended | |
|---|---|---|
|
Dec. 31, 2016
USD ($)
|
Dec. 31, 2015
USD ($)
a
ft²
|
|
| Organization, Consolidation and Presentation of Financial Statements [Abstract] | ||
| Area of land to be purchased for corporate offices | a | 1.6 | |
| Square feet of building to be purchased for corporate offices | ft² | 25 | |
| Total purchase price of land and building for future corporate offices | $ 1.8 | |
| Depreciation and amortization expense | $ 4.3 | $ 6.3 |